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Sample records for acidic crater lake

  1. Chemical hazards from acid crater lakes

    NASA Astrophysics Data System (ADS)

    van Bergen, M. J.; Sumarti, S.; Heikens, A.; Bogaard, T. A.; Hartiyatun, S.

    2003-04-01

    Acid crater lakes, which are hosted by a considerable number of active volcanoes, form a potential threat for local ecosystems and human health, as they commonly contain large amounts of dissolved chemicals. Subsurface seepage or overflow can lead to severe deterioration of the water quality of rivers and wells, as observations around several of these volcanoes have shown. The Ijen crater lake in East Java (Indonesia) is a striking example, as this reservoir of hyperacid (pH<0.5) sulphate, chloride and fluoride-rich water is the source of a ca. 50 km long acid river that transports substantial quantities of potentially toxic elements. A downstream trend of increasing pH from <1 to 2.5-4 is largely due to dilution with moderately acid springs (pH= ca. 4) and neutral tributaries (pH= ca. 7) inside the Ijen caldera. Geochemical controls that regulate element transport are subject to seasonal fluctuations in rainfall. Long-term monitoring has shown that fluoride levels pose some of the most severe environmental threats. Its concentration decreases from ca. 1300 mg/kg in the lake to ca. 10 mg/kg in a coastal area downstream, where virtually all of the river water is used for irrigating rice fields and other cropland. Apart from serious problems for agriculture, our survey of 55 drinking water wells in the irrigation area shows that 50% contain fluoride above the 1.5 ppm WHO limit, in line with the observation that dental fluorosis is widespread among the ca. 100,000 residents of the area. A conspicuous spatial correlation between fluoride concentrations and the irrigation system suggest that long-term (century) infiltration of irrigation water may have affected the quality of groundwater. Fluorosis is also a problem in some villages within the caldera, where well water sources may have a more direct subsurface connection with the lake system. From our observations we conclude that water-quality monitoring is especially needed for health reasons in volcanic areas where

  2. 2005 Crater Lake Formation, Lahar, Acidic Flood, and Gas Emission From Chiginagak Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Schaefer, J. R.; Scott, W. E.; McGimsey, R. G.; Jorgenson, J.

    2005-12-01

    A 400-m-wide crater lake developed in the formerly snow-and-ice-filled crater of Mount Chiginagak volcano sometime between August 2004 and June 2005, presumably due to increased heat flux from the hydrothermal system. We are also evaluating the possible role of magma intrusion and degassing. In early summer 2005, clay-rich debris and an estimated 5.6 million cubic meters of acidic water from the crater exited through tunnels in the base of a glacier that breaches the south crater rim. Over 27 kilometers downstream, the acidic waters of the flood reached approximately 1.5 meters above current water levels and inundated an important salmon spawning drainage, acidifying at least the surface water of Mother Goose Lake (approximately 1 cubic kilometer in volume) and preventing the annual salmon run. No measurements of pH were taken until late August 2005. At that time the pH of water sampled from the Mother Goose Lake inlet, lake surface, and outlet stream (King Salmon River) was 3.2. Defoliation and leaf damage of vegetation along affected streams, in areas to heights of over 70 meters in elevation above flood level, indicates that a cloud of detrimental gas or aerosol accompanied the flood waters. Analysis of stream water, lake water, and vegetation samples is underway to better determine the agent responsible for the plant damage. This intriguing pattern of gas-damaged vegetation concentrated along and above the flood channels is cause for further investigation into potential hazards associated with Chiginagak's active crater lake. Anecdotal evidence from local lodge owners and aerial photographs from 1953 suggest that similar releases occurred in the mid-1970s and early 1950s.

  3. Geochemistry, mineralogy, and chemical modeling of the acid crater lake of Kawah Ijen Volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Delmelle, Pierre; Bernard, Alain

    1994-06-01

    The Kawah Ijen volcano—with a record of phreatic eruptions—has its 1000 m wide crater filled with a lake that has existed for at least one century. At present, the lake waters are hot ( T ≈ 37° C), strongly mineralized (TDS = 105 g/L) and extremely acidic ( pH ≈ 0.4). By its volume, the Javanese lake is probably the largest accumulation in the world of such acidic waters. Mineralogy of the suspended solids within the lake waters suggests that concentrations of Si, Ca, Ti, and Ba are controlled by precipitation of silica, gypsum, anatase, and barite. Lake sediment is composed of chemical precipitates with composition similar to the suspended solids. Thermodynamic calculations predict that the lake waters have reached equilibrium with respect to α-cristobalite, barite, gypsum, anglesite, celestite, and amorphous silica, in agreement with the analytical observations. Significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized. Sulfides are absent in the water column but are always present in the native S spherules that form porous aggregates which float on the lake. The presence of native S provides direct evidence of more reduced conditions at the lake floor where H 2S is probably being injected into the lake. With progressive addition of H 2S to the acid waters, native S, pyrite, and enargite are theoretically predicted to be saturated. Reactions between upward streaming H 2S-bearing gases discharged by subaqueous fumaroles, and metals dissolved in the acidic waters could initiate precipitation of these sulfides. A model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake. Results show that strongly acidic, sulfate-rich solutions are formed under oxidizing conditions at high gas/water ratios. Reactions between the acidic fluids and the Ijen andesite were modeled to account for elevated cation concentrations in lake water. Current concentrations of conservative

  4. Crater Lake revealed

    USGS Publications Warehouse

    Ramsey, David W.; Dartnell, Peter; Bacon, Charles R.; Robinson, Joel E.; Gardner, James V.

    2003-01-01

    Around 500,000 people each year visit Crater Lake National Park in the Cascade Range of southern Oregon. Volcanic peaks, evergreen forests, and Crater Lake’s incredibly blue water are the park’s main attractions. Crater Lake partially fills the caldera that formed approximately 7,700 years ago by the eruption and subsequent collapse of a 12,000-foot volcano called Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama drastically changed the landscape all around the volcano and spread a blanket of volcanic ash at least as far away as southern Canada. Prior to the climactic event, Mount Mazama had a 400,000 year history of cone building activity like that of other Cascade volcanoes such as Mount Shasta. Since the climactic eruption, there have been several less violent, smaller postcaldera eruptions within the caldera itself. However, relatively little was known about the specifics of these eruptions because their products were obscured beneath Crater Lake’s surface. As the Crater Lake region is still potentially volcanically active, understanding past eruptive events is important to understanding future eruptions, which could threaten facilities and people at Crater Lake National Park and the major transportation corridor east of the Cascades. Recently, the lake bottom was mapped with a high-resolution multibeam echo sounder. The new bathymetric survey provides a 2m/pixel view of the lake floor from its deepest basins virtually to the shoreline. Using Geographic Information Systems (GIS) applications, the bathymetry data can be visualized and analyzed to shed light on the geology, geomorphology, and geologic history of Crater Lake.

  5. Gas flushing through hyper-acidic crater lakes: the next steps within a reframed monitoring time window

    NASA Astrophysics Data System (ADS)

    Rouwet, Dmitri

    2016-04-01

    Tracking variations in the chemical composition, water temperature and pH of brines from peak-activity crater lakes is the most obvious way to forecast phreatic activity. Volcano monitoring intrinsically implies a time window of observation that should be synchronised with the kinetics of magmatic processes, such as degassing and magma intrusion. To decipher "how much time ago" a variation in degassing regime actually occurred before eventually being detected in a crater lake is key, and depends on the lake water residence time. The above reasoning assumes that gas is preserved as anions in the lake water (SO4, Cl, F anions), in other words, that scrubbing of acid gases is complete and irreversible. Less is true. Recent work has confirmed, by direct MultiGas measurement from evaporative plumes, that even the strongest acid in liquid medium (i.e. SO2) degasses from hyper-acidic crater lakes. The less strong acid HCl has long been recognised as being more volatile than hydrophyle in extremely acidic solutions (pH near 0), through a long-term steady increase in SO4/Cl ratios in the vigorously evaporating crater lake of Poás volcano. We now know that acidic gases flush through hyper-acidic crater lake brines, but we don't know to which extend (completely or partially?), and with which speed. The chemical composition hence only reflects a transient phase of the gas flushing through the lake. In terms of volcanic surveillance this brings the advantage that the monitoring time window is definitely shorter than defined by the water chemistry, but yet, we do not know how much shorter. Empirical experiments by Capaccioni et al. (in press) have tried to tackle this kinetic problem for HCl degassing from a "lab-lake" on the short-term (2 days). With this state of the art in mind, two new monitoring strategies can be proposed to seek for precursory signals of phreatic eruptions from crater lakes: (1) Tracking variations in gas compositions, fluxes and ratios between species in

  6. Crater Lake: blue through time

    USGS Publications Warehouse

    Larson, Gary L.; Buktenica, Mark; Collier, Robert

    2003-01-01

    Blue is the color of constancy, hence the term true blue. The unearthly blueness of Crater Lake reflects its pristine character and gives scientists a focal point for studying human impacts on aquatic environments over long periods of time. Scientists with the U.S. Geological Survey (USGS), National Park Service, and Oregon State University have systematically studied the lake for the last two decades. Long-term monitoring of this lake is a priority of Crater Lake National Park and will continue far into the future.

  7. The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results

    USGS Publications Warehouse

    Schaefer, J.R.; Scott, W.E.; Evans, William C.; Jorgenson, J.; McGimsey, R.G.; Wang, B.

    2008-01-01

    A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8??106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfurcontent. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetationdamaging acidic aerosols accompanying drainage of an acidic crater

  8. The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results

    NASA Astrophysics Data System (ADS)

    Schaefer, Janet R.; Scott, William E.; Evans, William C.; Jorgenson, Janet; McGimsey, Robert G.; Wang, Bronwen

    2008-07-01

    A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8 × 106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfur content. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetation-damaging acidic aerosols accompanying drainage of an acidic

  9. Degassing of Aso Volcano, Japan through an Acid Crater Lake: Differentiation of Volcanic Gas-Hydrothermal Fluids Deduced from Volcanic Plume Chemistry

    NASA Astrophysics Data System (ADS)

    Shinohara, H.; Yoshikawa, S.; Miyabuchi, Y.

    2010-12-01

    Yudamari crater lake at Nakadake, Aso volcano, Japan is a hot and acid crater lake of 200-m-diameter. The active degassing occurs from a fumarolic area and through the crater lake, with SO2 emission of about 500 t/d. The fumarolic area locates at the southern wall of the crater lake shore and its activity is characterized by the high-temperature gas emission indicated by the red-glowing fumaroles. Degassing and evaporation are also intense from the crater lake surface. Since the crater lake is surrounded by steep slope, we cannot reach neither to the crater lake nor the fumarolic area for direct sampling. In order to characterize the degassing activity of these sources and evaluate differentiation process at volcanic-hydrothermal system beneath the crater lake, we conducted measurements of volcanic plumes to estimate composition of gases originating from the two gas sources; the crater lake (lake gas) and the high-temperature fumaroles (fumarolic gas) by the use of the Multi-GAS and alkaline-filter technique. Compositions of the lake gas and fumarolic gas are variable depending of the observation period, but the gases from the two sources have distinct compositions; fumarolic gases have higher CO2/SO2, HCl/SO2 and lower SO2/H2S ratio than the lake gases, but they have similar H2/CO2 ratios. The low HCl and H2S contents of the lake gases indicate the lake gases are derived by evaporation of the lake water, and their HCl/H2O ratios are consistent with this model. However, the high H2 and CO2 content in the lake gases also indicate that the lake gas is a mixture of bubbling gases and evaporation. The H2/CO2 ratio, which is less likely to be changed by dissolution into the lake water, is similar for the fumarolic gas and the lake gas, suggesting that both gases are derived from a common high-temperature fluid. The RH (=log(H2/H2O)) and SO2/H2S ratio of the fumarolic gases range from -2 to -3 and from10 to 30, respectively, corresponding to the apparent equilibrium

  10. Connections between hyper-acid crater lakes and flank springs: new evidence from Rincón de la Vieja volcano (Costa Rica)

    NASA Astrophysics Data System (ADS)

    Martínez, M.; Fernández, E.; Sáenz, W.; van Bergen, M. J.; Ayres, G.; Pacheco, J. F.; Brenes, J.; Avard, G.; Malavassi, E.

    2012-04-01

    Rincón de la Vieja, a complex andesitic stratovolcano in NW Costa Rica, shows various hydrothermal surface manifestations that comprise: (1) A hyper-acid crater lake and subaerial fumaroles receiving direct input of fluids of magmatic origin, (2) Acid thermal discharges along the northeastern slopes of the volcano that feed the headwaters of the Cucaracho river, and (3) Small lakes and a geothermal field with bubbling-boiling mud pools, acid-sulfate springs, steaming ground and fumarolic emissions in a region on the western flank. Here the streams are of relatively low flow rate and their chemical signatures correspond to that of deep fluids from an extensive geothermal reservoir mixed with shallow meteoric water. Physico-chemical properties of the sulfate-chloride hyper-acid lake (T=28-58 °C; pH between 1.2 and <0, high TDS of 24,000-160,000 mg/kg) are consistent with a meteoric water body supplied by a significant input of chemical components derived from hydrolysis of magmatic volatiles and from intense rock leaching. The Cucaracho catchment receives input from warm acid brines with no free-gas phase but carrying a high load of hydrolyzed magmatic volatiles and rock-forming elements. One of these brines (Spring 4) is characterized by a sulfate-chloride chemical signature, medium temperatures of 27-38 °C, pH between 2 and 4 and TDS values between 780 and 1300 mg/L. Based on water and heat-balance considerations, chemical and stable-isotope signatures and groundwater transport modeling, it has been proposed that these acid springs represent brine water from the lake-hydrothermal system that is diluted by shallow groundwater permeating tephra layers (Kempter and Rowe, 2000). Since Rincóńs latest phreatomagmatic activity in 1983, episodes of phreatic eruptions from the crater lake have been registered in 1983-87, 1991, 1995, 1998 and 2011. Some of these eruptions (VEI 1) have expelled large quantities of lake water, triggering small to medium- sized fast

  11. Unusual bacterioplankton community structure in ultra-oligotrophic Crater Lake

    USGS Publications Warehouse

    Urbach, Ena; Vergin, Kevin L.; Morse, Ariel

    2001-01-01

    The bacterioplankton assemblage in Crater Lake, Oregon (U.S.A.), is different from communities found in other oxygenated lakes, as demonstrated by four small subunit ribosomal ribonucleic acid (SSU rRNA) gene clone libraries and oligonucleotide probe hybridization to RNA from lake water. Populations in the euphotic zone of this deep (589 m), oligotrophic caldera lake are dominated by two phylogenetic clusters of currently uncultivated bacteria: CL120-10, a newly identified cluster in the verrucomicrobiales, and ACK4 actinomycetes, known as a minor constituent of bacterioplankton in other lakes. Deep-water populations at 300 and 500 m are dominated by a different pair of uncultivated taxa: CL500-11, a novel cluster in the green nonsulfur bacteria, and group I marine crenarchaeota. b-Proteobacteria, dominant in most other freshwater environments, are relatively rare in Crater Lake (<=16% of nonchloroplast bacterial rRNA at all depths). Other taxa identified in Crater Lake libraries include a newly identified candidate bacterial division, ABY1, and a newly identified subcluster, CL0-1, within candidate division OP10. Probe analyses confirmed vertical stratification of several microbial groups, similar to patterns observed in open-ocean systems. Additional similarities between Crater Lake and ocean microbial populations include aphotic zone dominance of group I marine crenarchaeota and green nonsulfur bacteria. Comparison of Crater Lake to other lakes studied by rRNA methods suggests that selective factors structuring Crater Lake bacterioplankton populations may include low concentrations of available trace metals and dissolved organic matter, chemistry of infiltrating hydrothermal waters, and irradiation by high levels of ultraviolet light.

  12. Impact of acid effluent from Kawah Ijen crater lake on irrigated agricultural soils: Soil chemical processes and plant uptake

    NASA Astrophysics Data System (ADS)

    van Rotterdam-Los, A. M. D.; Heikens, A.; Vriend, S. P.; van Bergen, M. J.; van Gaans, P. F. M.

    2008-12-01

    Volcanogenic contamination of irrigation water, caused by effluent from the hyperacid Ijen crater lake, has severely affected the properties of agricultural soils in East Java, Indonesia. From a comparison of acidified topsoil with subsoil and with top- and subsoil in a reference area, we identified processes responsible for changes in soil and soil solution chemistry induced by acid irrigation water, with emphasis on the nutrients Ca, Mg, Fe, and Mn, and on Al, which may become phytotoxic under acid conditions in soils. Compositional data for bulk soil composition and selective extractions with 1 M KCl and 0.2 M acid ammonium oxalate are used in a mass balance approach to specify element fluxes, including uptake by rice plants. The results show that input via irrigation water has produced an increase in the total aluminum content in the affected topsoil, which is of the same order of magnitude as the increase in labile Al. High bioavailability of Al, as reflected by concentrations in KCl extracts, is consistent with elevated concentrations observed in rice plants. In contrast, and despite the high input via irrigation water, Ca and Mg concentrations have decreased in all measured soil fractions through dissolution of amorphous phases and minerals, and through competition of Al for adsorption sites on the exchange complex and plant roots. Strong leaching is also evident for Fe and especially Mn. In terms of the overall mass balance of the topsoil, plant uptake of Al, Ca, Fe, Mg and Mn is negligible. If the use of acid irrigation would be stopped and the soil pH were to increase to values above 4.5, the observed phytotoxicity of Al will be halted. However, crops may then become fully dependent on the input from irrigation water or fertilizer for essential elements, due to the previous removal from the topsoil through leaching.

  13. Speciation: Genomic Archipelagos in a Crater Lake.

    PubMed

    Ronco, Fabrizia; Salzburger, Walter

    2016-03-01

    The opening stages of speciation remain poorly understood, especially from a genomic perspective. The genomes of newly discovered crater-lake cichlid fish shed light on the early phases of diversification and suggest that selection acts on multiple genomic regions.

  14. Crater lake colonization by neotropical cichlid fishes.

    PubMed

    Elmer, Kathryn R; Lehtonen, Topi K; Fan, Shaohua; Meyer, Axel

    2013-01-01

    Volcanic crater lakes are isolated habitats that are particularly well suited to investigating ecological and evolutionary divergence and modes of speciation. However, the mode, frequency, and timing of colonization of crater lakes have been difficult to determine. We used a statistical comparative phylogeographic approach, based on a mitochondrialDNA dataset, to infer the colonization history of two Nicaraguan crater lakes by populations of genetically and ecologically divergent cichlid lineages: Midas (Amphilophus cf. citrinellus complex) and moga (Hypsophrys nematopus). We compared estimates of diversity among populations within the two cichlid lineages and found that Midas were the most genetically diverse. From an approximate Bayesian computation analysis, we inferred that the crater lakes were each founded by both cichlid lineages in single waves of colonization: Masaya 5800 ± 300 years ago and Xiloá 5400 ± 750 years ago. We conclude that natural events are likely to have a dominant role in colonization of the crater lakes. Further, our findings suggest that the higher species richness and more rapid evolution of the Midas species complex, relative to other lineages of fishes in the same crater lakes, cannot be explained by earlier or more numerous colonization events.

  15. The Lake Bosumtwi impact crater, Ghana

    USGS Publications Warehouse

    Jones, William B.; Bacon, Michael; Hastings, David A.

    1981-01-01

    Analogy with better-known craters suggests that Bosumtwi has a central uplift rising to 200 m beneath the lake floor. An aeromagnetic anomaly of amplitude 50 nanotesla (nT) over the northern half of the lake is interpreted as due to a layer of magnetized fallback breccia beneath the lake sediments. The normal polarity of the breccia shows that the crater was formed during the normal Jaramillo event of 0.97 to 0.85 m.y. ago, which agrees with the magnetic stratigraphy of the related Ivory Coast microtektites. A regional gravity survey indicates a negative Bouguer anomaly over the crater. There is some geochemical evidence that the meteorite was an iron, and its mass and energy are suggested as about 108 tons and 3 × 1019 joules or 7.3 × 103 megatons.

  16. Speciation: Genomic Archipelagos in a Crater Lake.

    PubMed

    Ronco, Fabrizia; Salzburger, Walter

    2016-03-01

    The opening stages of speciation remain poorly understood, especially from a genomic perspective. The genomes of newly discovered crater-lake cichlid fish shed light on the early phases of diversification and suggest that selection acts on multiple genomic regions. PMID:26954438

  17. Overview of the limnology of crater lake

    USGS Publications Warehouse

    Larson, G.L.

    1996-01-01

    Crater Lake occupies the collapsed caldera of volcanic Mount Mazama in Crater Lake National Park, Oregon. It is the deepest lake (589 m) in the United States and the 7th deepest lake in the world. The water column mixes to a depth of about 200 m in winter and spring from wind energy and cooling. The deep lake is mixed in winter and early spring each year when relatively cold water near the surface sinks and exchanges positions with water in the deep basins of the lake. The lake becomes thermally stratified in summer and early fall. The metalimnion extends to a depth of about 100 m; thus most of the water column is a cold hypolimnion. Secchi disk clarity measurements typically are in the upper-20-m range to the low-30-m range in summer and early fall. Concentrations of nutrients are low, although conductivity is relatively high owing to the inflow of hydrothermal fluids. Total chlorophyll is low in concentration, but typically maximal at a depth of 120 m during periods of thermal stratification. Primary production also is low, with the maximum levels occurring between the depth of 40 and 80 m. Phytoplankton taxa are spatially segregated from each other within the water column to a depth of 200 m in summer and early fall. The same generalization applies to the Zooplankton taxa. Water level, clarity, concentrations of total chlorophyll, primary production, and abundances of zooplankton and introduced kokanee salmon exhibit long-term fluctuations. Based primarily on a recent 10-year study of the lake, the lake is considered to be pristine, except for the consequences of fish introductions. ?? 1996 by the Northwest Scientific Association. All rights reserved.

  18. Overview of the limnology of Crater Lake

    USGS Publications Warehouse

    Larson, Gary L.

    1996-01-01

    Crater Lake occupies the collapsed caldera of volcanic Mount Mazama in Crater Lake National Park, Oregon. It is the deepest lake (589 m) in the United States and the 7th deepest lake in the world. The water column mixes to a depth of about 200 m in winter and spring from wind energy and cooling. The deep lake is mixed in winter and early spring each year when relatively cold water near the surface sinks and exchanges positions with water in the deep basins of the lake. The lake becomes thermally stratified in summer and early fall. The metalimnion extends to a depth of about 100 m; thus most of the water column is a cold hypolimnion. Secchi disk clarity measurements typically are in the upper-20-m range to the low-30-m range in summer and early fall. Concentrations of nutrients are low, although conductivity is relatively high owing to the inflow of hydrothermal fluids. Total chlorophyll is low in concentration, but typically maximal at a depth of 120 m during periods of thermal stratification. Primary production also is low, with the maximum levels occurring between the depth of 40 and 80 m. Phytoplankton taxa are spatially segregated from each other within the water column to a depth of 200 m in summer and early fall. The same generalization applies to the zooplankton taxa. Water level, clarity, concentrations of total chlorophyll, primary production, and abundances of zooplankton and introduced kokanee salmon exhibit long-term fluctuations. Based primarily on a recent 10-year study of the lake, the lake is considered to be pristine, except for the consequences of fish introductions.

  19. 36 CFR 7.2 - Crater Lake National Park.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Crater Lake National Park. 7.2 Section 7.2 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.2 Crater Lake National Park. (a)...

  20. Crater Lake Revealed: Using GIS to Visualize and Analyze Postcaldera Volcanoes Beneath Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Ramsey, D. W.; Robinson, J. E.; Dartnell, P.; Bacon, C. R.; Gardner, J. V.; Mayer, L. A.; Buktenica, M. W.

    2001-12-01

    Crater Lake, Oregon, partially fills the caldera that formed ~7,700 years ago by the eruption of 50 km3 of mainly rhyodacitic magma and collapse of Mount Mazama. Prior to the climactic event, Mount Mazama had a 400,000-year eruptive history, much of which was like those of other Cascade volcanic centers such as Mount Shasta. Since the climactic eruption, there have been several less violent, smaller eruptions within the caldera itself. Until a recent bathymetric survey, relatively little was known about the character and timing of these eruptions because their products are obscured beneath Crater Lake's surface. In the summer of 2000, the lake bottom was mapped with a high-resolution multibeam echo sounder (Gardner et. al., 2001), providing a 2m/pixel view of the lake floor from its deepest basins virtually to the shoreline. Using Geographic Information Systems (GIS) applications, the bathymetric data has been visualized and analyzed (aided by images and samples obtained with the manned submersible Deep Rover, sediment cores and dredged rocks, and detailed geologic mapping of Mount Mazama) to determine a geologic map of the lake bottom, a history of lake filling (Nathenson et. al., 2001), and volumes, times, and rates of postcaldera eruptions. These calculations have been used to assemble a geologic history for Crater Lake from the time of caldera formation to present day. Postcaldera eruptions have been both subareal and subaqueous, and were well underway within about 90 years after the climactic eruption, beginning with andesitic lava flows from the Wizard Island and central platform volcanoes. The eruptive history of the Wizard Island volcano is divided into three periods defined by former shorelines where subaerial flows entered the lake, quenched rapidly, and fractured, forming lobate deltas and breccia slopes. The shorelines are visible in slope and shaded-relief images of the lake floor created with GIS. The lake filling model suggests that these shorelines

  1. Representative freshwater bacterioplankton isolated from Crater Lake, Oregon.

    PubMed

    Page, Kathleen A; Connon, Stephanie A; Giovannoni, Stephen J

    2004-11-01

    High-throughput culturing (HTC) methods that rely on dilution to extinction in very-low-nutrient media were used to obtain bacterial isolates from Crater Lake, Oregon. 16S rRNA sequence determination and phylogenetic reconstruction were used to determine the potential ecological significance of isolated bacteria, both in Crater Lake and globally. Fifty-five Crater Lake isolates yielded 16 different 16S rRNA gene sequences. Thirty of 55 (55%) Crater Lake isolates had 16S rRNA gene sequences with 97% or greater similarity to sequences recovered previously from Crater Lake 16S rRNA gene clone libraries. Furthermore, 36 of 55 (65%) Crater Lake isolates were found to be members of widely distributed freshwater groups. These results confirm that HTC is a significant improvement over traditional isolation techniques that tend to enrich for microorganisms that do not predominate in their environment and rarely correlate with 16S rRNA gene clone library sequences. Although all isolates were obtained under dark, heterotrophic growth conditions, 2 of the 16 different groups showed evidence of photosynthetic capability as assessed by the presence of puf operon sequences, suggesting that photoheterotrophy may be a significant process in this oligotrophic, freshwater habitat.

  2. Volcano and earthquake hazards in the Crater Lake region, Oregon

    USGS Publications Warehouse

    Bacon, Charles R.; Mastin, Larry G.; Scott, Kevin M.; Nathenson, Manuel

    1997-01-01

    Crater Lake lies in a basin, or caldera, formed by collapse of the Cascade volcano known as Mount Mazama during a violent, climactic eruption about 7,700 years ago. This event dramatically changed the character of the volcano so that many potential types of future events have no precedent there. This potentially active volcanic center is contained within Crater Lake National Park, visited by 500,000 people per year, and is adjacent to the main transportation corridor east of the Cascade Range. Because a lake is now present within the most likely site of future volcanic activity, many of the hazards at Crater Lake are different from those at most other Cascade volcanoes. Also significant are many faults near Crater Lake that clearly have been active in the recent past. These faults, and historic seismicity, indicate that damaging earthquakes can occur there in the future. This report describes the various types of volcano and earthquake hazards in the Crater Lake area, estimates of the likelihood of future events, recommendations for mitigation, and a map of hazard zones. The main conclusions are summarized below.

  3. Gale Crater: An Amazonian Impact Crater Lake at the Plateau/Plain Boundary

    NASA Technical Reports Server (NTRS)

    Cabrol, N. A.; Grin, E. A.

    1998-01-01

    sedimentary material that can originate both from drainage of the regional subsurface aquifer, and/or from surface flood. The central deposit shows three main levels: (a) the current crater floor (north of Gale), (b) an ancient level about 200 rn higher (south of Gale), and (c) the massive terraced deposits. A crater statistics on the 15,400 kM2 area of the crater floor and deposit [3,41 gave: 259+/-112.4 craters, most of them partly embayed in the sedimentary deposit, and all inferior to 5-km diameter. For superimposed crater population only, the result is 194+/-112. The deduced relative ages ranges from Early to Middle Amazonian. The population of craters are comparable for the three levels, implying that the last sedimentation/erosion episode on Gale was recent and affected the whole crater. The streamlined morphology of the border of the deposit, the layering, the channels, and the terraces are compatible with a significant fluvio-lacustrine history of the site. Multiple levels may suggest different episodes, but the common statistical age of the three levels shows that the last episode involved the whole crater. The origin of the lake water in Gale may have varied in time. Three major contributions have been proposed: (a) the drainage of the regional underground aquifer by Gale crater over an area of 110-km radius around the crater which would have provided approximately 1,600 cubic km of water, (b), surface drainage entering Gale by the south and north rims. In the south, a 250-km long system originates in the cratered uplands in a Noachian crater material plain (Nc), and crosses Hesperian and Amazonian crater material plains (AHc) northward [1]. Several fluvial systems originate in the Aeolis Mensae, east of Gale. They may had two functions in time: to recharge, the underground aquifer in the region of Gale, and to supply surface water in the crater by overspilling the northern rim, and (c) surface floods that originated from the rising of the water level in the

  4. Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

    USGS Publications Warehouse

    Bacon, Charles R.

    2008-01-01

    Crater Lake partly fills one of the most spectacular calderas of the world, an 8-by-10-km basin more than 1 km deep formed by collapse of the volcano known as Mount Mazama (fig. 1) during a rapid series of explosive eruptions about 7,700 years ago. Having a maximum depth of 594 m, Crater Lake is the deepest lake in the United States. Crater Lake National Park, dedicated in 1902, encompasses 645 km2 of pristine forested and alpine terrain, including the lake itself, virtually all of Mount Mazama, and most of the area of the geologic map. The geology of the area was first described in detail by Diller and Patton (1902) and later by Williams (1942), whose vivid account led to international recognition of Crater Lake as the classic collapse caldera. Because of excellent preservation and access, Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. For example, the climactic ejecta are renowned among volcanologists as evidence for systematic compositional zonation within a subterranean magma chamber. Mount Mazama's climactic eruption also is important as the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore. A detailed bathymetric survey of the floor of Crater Lake in 2000 (Bacon and others, 2002) provides a unique record of postcaldera eruptions, the interplay between volcanism and filling of the lake, and sediment transport within this closed basin. Knowledge of the geology and eruptive history of the Mount Mazama edifice, greatly enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve. Lastly, the many smaller volcanoes of the High Cascades beyond the limits of Mount Mazama are a source of information on the flux of mantle-derived magma through the region. General principles of magmatic and eruptive

  5. Crater lake and post-eruption hydrothermal activity, El Chichón Volcano, Mexico

    USGS Publications Warehouse

    Casadevall, Thomas J.; de la Cruz-Reyna, Servando; Rose, William I.; Bagley, Susan; Finnegan, David L.; Zoller, William H.

    1984-01-01

    Explosive eruptions of Volcán El Chichón in Chiapas, Mexico on March 28 and April 3–4, 1982 removed 0.2 km3 of rock to form a 1-km-wide 300-m-deep summit crater. By late April 1982 a lake had begun to form on the crater floor, and by November 1982 it attained a maximum surface area of 1.4 × 105 m2 and a volume of 5 × 106 m3. Accumulation of 4–5 m of rainfall between July and October 1982 largely formed the lake. In January 1983, temperatures of fumaroles on the crater floor and lower crater walls ranged from 98 to 115°C; by October 1983 the maximum temperature of fumarole emissions was 99°C. In January 1983 fumarole gas emissions were greater than 99 vol. % H2O with traces of CO2, SO2, and H2S. The water of the lake was a hot (T = 52–58°C), acidic (pH = 0.5), dilute solution (34,046 mg L−1 dissolved solids; Cl/S = 20.5). Sediment from the lake contains the same silicate minerals as the rocks of the 1982 pyroclastic deposits, together with less than 1% of elemental sulfur. The composition and temperature of the lake water is attributed to: (1) solution of fumarole emissions; (2) reaction of lake water with hot rocks beneath the lake level; (3) sediments washed into the lake from the crater walls; (4) hydrothermal fluids leaching sediments and formational waters in sedimentary rocks of the basement; (5) evaporation; and (6) precipitation.

  6. Seismic investigation of the Lake Bosumtwi impact crater: preliminary results

    NASA Astrophysics Data System (ADS)

    Karp, Tobias; Milkereit, Bernd; Janle, Peter; Danuor, Sylvester K.; Pohl, Jean; Berckhemer, Hans; Scholz, Christopher A.

    2002-06-01

    The Lake Bosumtwi impact crater in Ghana, West Africa, has a diameter of 10.5 km and is one of the youngest ( 1.07 Ma) well-preserved large craters on Earth. It has a total dynamic range of topography of more than 400 m, and it is the source crater of tektites and microtektites of the Ivory Coast strewn field. The crater was excavated in early Proterozoic rocks. According to its size, the Bosumtwi impact crater should be a complex impact structure, with a central peak. Multichannel seismic (MCS) reflection and wide angle data, using Ocean-Bottom-Hydrophones (OBHs), were acquired in order to investigate the structure's subsurface, image the presumed central uplift and determine the thickness of impact-related formations and the post-impact sediments. An integrated interpretation of the seismic data sets, and modelling and inversion of the OBH data yield an initial 2D velocity-depth model, which shows indications for a central peak feature. Due to the relatively low seismic velocity ( 3.0 km s -1) of the corresponding layer, the top of the uplifted structure is interpreted to consist of allochthonous breccia. The central peak has a width of ˜1.8 km and a maximum height of 120 m above the top of the breccia away from the center. Fracturing may be responsible for the relatively low velocity of 3.8 km s -1 in the crater floor. The post-impact sediments covering the crater structure are 180- 300 m thick. The apparent crater depth, defined as the difference between the original target surface and the top of the breccia layer, is ˜550 m and thereby slightly deeper than some other larger complex impact structures on Earth. The results indicate that the Lake Bosumtwi impact structure provides an interesting setting for scientific drilling of a young large impact crater and will be supplemented by complimentary recent geophysical (potential field) and possibly future drilling studies.

  7. Groundwater transport of crater-lake brine at Poas Volcano, Costa Rica

    USGS Publications Warehouse

    Sanford, W.E.; Konikow, L.F.; Rowe, G.L.; Brantley, S.L.

    1995-01-01

    This study analyzes the regional groundwater system at Poas and demonstrates the likelihood that the water discharging from the acidic springs in the Rio Agrio watershed originates at the acidic crater lake. Both heat and solute transport are analyzed on a regional scale through numerical simulations using the HST3D finite-difference model, which solves the coupled equations for fluid flow, heat transport, and solute transport. The code allows fluid viscosity and density to be functions of both temperature and solute concentration. The simulations use estimates for recharge to the mountain and a range of values and various distributions of permeability and porosity. Several sensitivity analyses are performed to test how the uncertainty in many of the model parameters affects the simulation results. These uncertainties yield an estimated range of travel times from the crater lake to the Rio Agrio springs of 1-30 yr, which is in close agreement with the results of tritium analyses of the springs. Calculated groundwater fluxes into and out of the crater lake are both about several hundred kg/s. These fluxes must be accounted for in water budgets of the crater lake. -from Authors

  8. Models for the Filling of Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Nathenson, M.; Bacon, C. R.; Gardner, J. V.

    2001-12-01

    Crater Lake partially fills, to a depth of 593 m, the 10-km-diameter, 1200-m-deep caldera formed by collapse of Mount Mazama volcano. The lake receives water from direct precipitation and inflow from the caldera walls and loses water by surface evaporation and leakage. No streams flow from Crater Lake. A high-resolution multibeam echo sounding survey of the lake floor conducted in 2000 (Gardner et al., 2001) revealed seven drowned beaches between 1849 and 1878 m elevation (reference lake elevation is 1883 m). The beaches are thought to reflect drier periods in the lake's history since the climactic, caldera-forming eruption of Mount Mazama, approximately 7,700 years ago. The shallowest drowned beach at 1878 m represents the deepest part of a wave-cut platform up to 100 m wide, substantially wider than any of the beaches, where erodible talus or intensely altered rocks are present. The great width of the platform compared to the width of the drowned beaches indicates that the lake has mostly been near its current level during the lake's history. Unambiguous evidence of former highstands above 1883 m has not been reported. In order to explain the occurrence of the drowned beaches and their relatively narrow depth range, leakage through the caldera walls must vary with depth and cannot occur just at the lake bottom or at the modern lake level. A reasonable model is that leakage is proportional to elevation above the bottom of the lake. Recognition that there is a thick layer of relatively permeable debris resting on glaciated lava in the northeast caldera wall above an elevation of 1845 m suggests a variant of this model where leakage is proportional to elevation above 1845 m. Climate studies indicate that Crater Lake began to fill during a dry period. Assuming that precipitation at that time was 70% of modern and that the beach at 1853 m (the deeper beach is somewhat suspect) corresponds to this amount of precipitation, a combination of the above leakage models is

  9. Paenibacillus baekrokdamisoli sp. nov., isolated from soil of crater lake.

    PubMed

    Lee, Keun Chul; Kim, Kwang Kyu; Kim, Jong-Shik; Kim, Dae-Shin; Ko, Suk-Hyung; Yang, Seung-Hoon; Lee, Jung-Sook

    2016-05-01

    A novel bacterial strain, Back-11T, was isolated from sediment soil of a crater lake, Baekrokdam, Hallasan, Jeju, Republic of Korea. Cells of strain Back-11T were Gram-stain-positive, motile, endospore-forming, rod-shaped and oxidase- and catalase-positive. It contained anteiso-C15 : 0 as the major fatty acid, menaquinone-7 (MK-7) as the predominant isoprenoid quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and four unidentified aminophospholipids as the main polar lipids, and meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 45.3 mol%. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain Back-11T was most closely related to Paenibacillus taihuensis THMBG22T (95.5 % similarity) and fell into a clade in the genus Paenibacillus. On the basis of phylogenetic, chemotaxonomic and phenotypic data, strain Back-11T represents a novel species in the genus Paenibacillus, for which the name Paenibacillus baekrokdamisoli sp. nov. is proposed. The type strain is Back-11T ( = KCTC 33723T = CECT 8890T). PMID:26868819

  10. Paenibacillus baekrokdamisoli sp. nov., isolated from soil of crater lake.

    PubMed

    Lee, Keun Chul; Kim, Kwang Kyu; Kim, Jong-Shik; Kim, Dae-Shin; Ko, Suk-Hyung; Yang, Seung-Hoon; Lee, Jung-Sook

    2016-05-01

    A novel bacterial strain, Back-11T, was isolated from sediment soil of a crater lake, Baekrokdam, Hallasan, Jeju, Republic of Korea. Cells of strain Back-11T were Gram-stain-positive, motile, endospore-forming, rod-shaped and oxidase- and catalase-positive. It contained anteiso-C15 : 0 as the major fatty acid, menaquinone-7 (MK-7) as the predominant isoprenoid quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and four unidentified aminophospholipids as the main polar lipids, and meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 45.3 mol%. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain Back-11T was most closely related to Paenibacillus taihuensis THMBG22T (95.5 % similarity) and fell into a clade in the genus Paenibacillus. On the basis of phylogenetic, chemotaxonomic and phenotypic data, strain Back-11T represents a novel species in the genus Paenibacillus, for which the name Paenibacillus baekrokdamisoli sp. nov. is proposed. The type strain is Back-11T ( = KCTC 33723T = CECT 8890T).

  11. Under trees and water at Crater Lake National Park, Oregon

    USGS Publications Warehouse

    Robinson, Joel E.; Bacon, Charles R.; Wayne, Chris

    2012-01-01

    Crater Lake partially fills the caldera that formed approximately 7,700 years ago during the eruption of a 12,000-ft-high volcano known as Mount Mazama. The caldera-forming, or climactic, eruption of Mount Mazama devastated the surrounding landscape, left a thick deposit of pumice and ash in adjacent valleys, and spread a blanket of volcanic ash as far away as southern Canada. Prior to the climactic event, Mount Mazama had a 400,000-year history of volcanic activity similar to other large Cascade volcanoes such as Mounts Shasta, Hood, and Rainier. Since the caldera formed, many smaller, less violent eruptions occurred at volcanic vents below Crater Lake's surface, including Wizard Island. A survey of Crater Lake National Park with airborne LiDAR (Light Detection And Ranging) resulted in a digital elevation map of the ground surface beneath the forest canopy. The average resolution is 1.6 laser returns per square meter yielding vertical and horizontal accuracies of ±5 cm. The map of the floor beneath the surface of the 1,947-ft-deep (593-m-deep) Crater Lake was developed from a multibeam sonar bathymetric survey and was added to the map to provide a continuous view of the landscape from the highest peak on Mount Scott to the deepest part of Crater Lake. Four enlarged shaded-relief views provide a sampling of features that illustrate the resolution of the LiDAR survey and illustrate its utility in revealing volcanic landforms and subtle features of the climactic eruption deposits. LiDAR's high precision and ability to "see" through the forest canopy reveal features that may not be easily recognized-even when walked over-because their full extent is hidden by vegetation, such as the 1-m-tall arcuate scarp near Castle Creek.

  12. The Geology and Petrography of Crater Lake National Park

    USGS Publications Warehouse

    Diller, Joseph Silas; Patton, Horace Bushnell

    1902-01-01

    Origin of the name Mount Mazama - A great impetus to the spread of information concerning Crater Lake was given by the Mazamas of Portland, Oreg., who held a meeting at the lake in August, 1896, which attracted many visitors. The principal features in the history of the lake had previously been made out, and the Mazamas, recognizing the fact that the great peak which was nearly destroyed in preparing the pit for the lake had no name, gave it the name of their own society. Upon the rim of the lake are a number of small peaks, each having its own designation. The term Mount Mazama refers to the whole rim encircling the lake. It is but a mere remnant of the once lofty peak, the real Mount Mazama, which rose far into the region of eternal snow. To get a basis for reconstructing the original Mount Mazama it is necessary to study in detail the structure and composition of its foundation, now so attractively displayed in the encircling cliffs of Crater Lake.

  13. Subaqueous geology and a filling model for Crater Lake, Oregon

    USGS Publications Warehouse

    Nathenson, M.; Bacon, C.R.; Ramsey, D.W.

    2007-01-01

    Results of a detailed bathymetric survey of Crater Lake conducted in 2000, combined with previous results of submersible and dredge sampling, form the basis for a geologic map of the lake floor and a model for the filling of Crater Lake with water. The most prominent landforms beneath the surface of Crater Lake are andesite volcanoes that were active as the lake was filling with water, following caldera collapse during the climactic eruption of Mount Mazama 7700 cal. yr B.P. The Wizard Island volcano is the largest and probably was active longest, ceasing eruptions when the lake was 80 m lower than present. East of Wizard Island is the central platform volcano and related lava flow fields on the caldera floor. Merriam Cone is a symmetrical andesitic volcano that apparently was constructed subaqueously during the same period as the Wizard Island and central platform volcanoes. The youngest postcaldera volcanic feature is a small rhyodacite dome on the east flank of the Wizard Island edifice that dates from 4800 cal. yr B.P. The bathymetry also yields information on bedrock outcrops and talus/debris slopes of the caldera walls. Gravity flows transport sediment from wall sources to the deep basins of the lake. Several debris-avalanche deposits, containing blocks up to 280 m long, are present on the caldera floor and occur below major embayments in the caldera walls. Geothermal phenomena on the lake floor are bacterial mats, pools of solute-rich warm water, and fossil subaqueous hot spring deposits. Lake level is maintained by a balance between precipitation and inflow versus evaporation and leakage. High-resolution bathymetry reveals a series of up to nine drowned beaches in the upper 30 m of the lake that we propose reflect stillstands subsequent to filling of Crater Lake. A prominent wave-cut platform between 4 m depth and present lake level that commonly is up to 40 m wide suggests that the surface of Crater Lake has been at this elevation for a very long time

  14. Detecting long-term hydrological patterns at Crater Lake, Oregon

    USGS Publications Warehouse

    Peterson, D.L.; Silsbee, D.G.; Redmond, Kelly T.

    1999-01-01

    Tree-ring chronologies for mountain hemlock (Tsuga mertensiana) were used to reconstruct the water level of Crater Lake, a high-elevation lake in the southern Cascade Range of Oregon. Reconstructions indicate that lake level since the late 1980s has been lower than at any point in the last 300 years except the early 1930s to mid 1940s. Lake level was consistently higher during the Little Ice Age than during the late 20th century; during the late 17th century, lake level was up to 9 m higher than recent (1980s and 1990s) low levels, which is consistent with paleoclimalic reconstructions of regional precipitation and atmospheric pressure. Furthermore, instrumental data available for the 20th century suggest that there are strong teleconnections among atmospheric circulation (e.g., Pacific Decadal Oscillation), tree growth, and hydrology in southern Oregon. Crater Lake is sensitive to interannual, interdecadal and intercentenary variation in precipitation and atmospheric circulation, and can be expected to track both short-term and longterm variation in regional climatic patterns that may occur in the future.

  15. Effect of glacier ablation on the Snettisham Hydroelectric Project, Long Lake and Crater Lake Basins, Alaska

    USGS Publications Warehouse

    Sloan, C.E.; Emery, P.A.; Fair, Diana

    1986-01-01

    Long Lake Basin in the Snettisham Project Area southeast of Juneau, Alaska, yields water used for the production of hydroelectric power. Development of adjacent Crater Lake is planned to increase the Project 's generating capacity. Estimates of the hydroelectric potential of the lakes are based on streamflow records which are influenced by glaciers that cover 25% of the combined basins. Analysis of streamflow records shows that the quality and extent of records in the area are sufficient to predict flow from the Crater Creek basin with a fairly high degree of confidence. Comparison of aerial photographs indicates that glacier ablation and recession have been continuous since at least 1929. Estimates of ice-volume change from photogrammetric measurements indicate that less than 2.5% of the average runoff from the basins of Long and Crater Lakes has been from reduction in glacier-ice storage. (Author 's abstract)

  16. Leakage of active crater lake brine through the north flank at Rincon de la Vieja volcano, northwest Costa Rica, and implications for crater collapse

    USGS Publications Warehouse

    Kempter, K.A.; Rowe, G.L.

    2000-01-01

    The Active Crater at Rincon de la Vieja volcano, Costa Rica, reaches an elevation of 1750 m and contains a warm, hyper-acidic crater lake that probably formed soon after the eruption of the Rio Blanco tephra deposit approximately 3500 years before present. The Active Crater is buttressed by volcanic ridges and older craters on all sides except the north, which dips steeply toward the Caribbean coastal plains. Acidic, above-ambient-temperature streams are found along the Active Crater's north flank at elevations between 800 and 1000 m. A geochemical survey of thermal and non-thermal waters at Rincon de la Vieja was done in 1989 to determine whether hyper-acidic fluids are leaking from the Active Crater through the north flank, affecting the composition of north-flank streams. Results of the water-chemistry survey reveal that three distinct thermal waters are found on the flanks of Rincon de la Vieja volcano: acid chloride-sulfate (ACS), acid sulfate (AS), and neutral chloride (NC) waters. The most extreme ACS water was collected from the crater lake that fills the Active Crater. Chemical analyses of the lake water reveal a hyper-acidic (pH ~ 0) chloride-sulfate brine with elevated concentrations of calcium, magnesium, aluminum, iron, manganese, copper, zinc, fluorine, and boron. The composition of the brine reflects the combined effects of magmatic degassing from a shallow magma body beneath the Active Crater, dissolution of andesitic volcanic rock, and evaporative concentration of dissolved constituents at above-ambient temperatures. Similar cation and anion enrichments are found in the above-ambient-temperature streams draining the north flank of the Active Crater. The pH of north-flank thermal waters range from 3.6 to 4.1 and chloride:sulfate ratios (1.2-1.4) that are a factor of two greater than that of the lake brine (0.60). The waters have an ACS composition that is quite different from the AS and NC thermal waters that occur along the southern flank of Rincon

  17. Leakage of Active Crater lake brine through the north flank at Rincón de la Vieja volcano, northwest Costa Rica, and implications for crater collapse

    NASA Astrophysics Data System (ADS)

    Kempter, K. A.; Rowe, G. L.

    2000-04-01

    The Active Crater at Rincón de la Vieja volcano, Costa Rica, reaches an elevation of 1750 m and contains a warm, hyper-acidic crater lake that probably formed soon after the eruption of the Rio Blanco tephra deposit approximately 3500 years before present. The Active Crater is buttressed by volcanic ridges and older craters on all sides except the north, which dips steeply toward the Caribbean coastal plains. Acidic, above-ambient-temperature streams are found along the Active Crater's north flank at elevations between 800 and 1000 m. A geochemical survey of thermal and non-thermal waters at Rincón de la Vieja was done in 1989 to determine whether hyper-acidic fluids are leaking from the Active Crater through the north flank, affecting the composition of north-flank streams. Results of the water-chemistry survey reveal that three distinct thermal waters are found on the flanks of Rincón de la Vieja volcano: acid chloride-sulfate (ACS), acid sulfate (AS), and neutral chloride (NC) waters. The most extreme ACS water was collected from the crater lake that fills the Active Crater. Chemical analyses of the lake water reveal a hyper-acidic ( pH˜0) chloride-sulfate brine with elevated concentrations of calcium, magnesium, aluminum, iron, manganese, copper, zinc, fluorine, and boron. The composition of the brine reflects the combined effects of magmatic degassing from a shallow magma body beneath the Active Crater, dissolution of andesitic volcanic rock, and evaporative concentration of dissolved constituents at above-ambient temperatures. Similar cation and anion enrichments are found in the above-ambient-temperature streams draining the north flank of the Active Crater. The pH of north-flank thermal waters range from 3.6 to 4.1 and chloride:sulfate ratios (1.2-1.4) that are a factor of two greater than that of the lake brine (0.60). The waters have an ACS composition that is quite different from the AS and NC thermal waters that occur along the southern flank of

  18. Distribution, Classification, and Ages of Martian Impact Crater Lakes

    NASA Astrophysics Data System (ADS)

    Cabrol, Nathalie A.; Grin, Edmond A.

    1999-11-01

    Paleolakes in impact craters on Mars are characterized at global scale using the Viking Orbiter data. We identified 179 paleolakes in impact structures formed by the influx of water and sediment derived from valley networks and channels that can be classified into three different fluviolacustrine systems: closed, open, and lake-chain systems. We show the hydrogeologic implications for each of the three systems and their significance in terms of duration of fluviolacustrine activity. This study provides a catalog of areographic, physical, and physiographic data for each of the studied impact crater lakes, associated with the description of the sedimentary structures observed. It also identifies environments where life and/or precursors to life could have found favorable conditions to evolve.

  19. Thermal, chemical, and optical properties of Crater Lake, Oregon

    USGS Publications Warehouse

    Larson, G.L.; Hoffman, R.L.; McIntire, D.C.; Buktenica, M.W.; Girdner, S.F.

    2007-01-01

    Crater Lake covers the floor of the Mount Mazama caldera that formed 7700 years ago. The lake has a surface area of 53 km2 and a maximum depth of 594 m. There is no outlet stream and surface inflow is limited to small streams and springs. Owing to its great volume and heat, the lake is not covered by snow and ice in winter unlike other lakes in the Cascade Range. The lake is isothermal in winter except for a slight increase in temperature in the deep lake from hyperadiabatic processes and inflow of hydrothermal fluids. During winter and spring the water column mixes to a depth of about 200-250 m from wind energy and convection. Circulation of the deep lake occurs periodically in winter and spring when cold, near-surface waters sink to the lake bottom; a process that results in the upwelling of nutrients, especially nitrate-N, into the upper strata of the lake. Thermal stratification occurs in late summer and fall. The maximum thickness of the epilimnion is about 20 m and the metalimnion extends to a depth of about 100 m. Thus, most of the lake volume is a cold hypolimnion. The year-round near-bottom temperature is about 3.5??C. Overall, hydrothermal fluids define and temporally maintain the basic water quality characteristics of the lake (e.g., pH, alkalinity and conductivity). Total phosphorus and orthophosphate-P concentrations are fairly uniform throughout the water column, where as total Kjeldahl-N and ammonia-N are highest in concentration in the upper lake. Concentrations of nitrate-N increase with depth below 200 m. No long-term changes in water quality have been detected. Secchi disk (20-cm) clarity varied seasonally and annually, but was typically highest in June and lowest in August. During the current study, August Secchi disk clarity readings averaged about 30 m. The maximum individual clarity reading was 41.5 m in June 1997. The lowest reading was 18.1 m in July 1995. From 1896 (white-dinner plate) to 2003, the average August Secchi disk reading was

  20. Hydrology of Crater, East and Davis Lakes, Oregon; with section on Chemistry of the Lakes

    USGS Publications Warehouse

    Phillips, Kenneth N.; Van Denburgh, A.S.

    1968-01-01

    Crater, East, and Davis Lakes are small bodies of fresh water that occupy topographically closed basins in Holocene volcanic terrane. Because the annual water supply exceeds annual evaporation, water must be lost by seepage from each lake. The seepage rates vary widely both in volume and in percentage of the total water supply. Crater Lake loses about 89 cfs (cubic feet per second), equivalent to about 72 percent of its average annual supply. East Lake loses about 2.3 cfs, or about 44 percent of its estimated supply. Davis Lake seepage varies greatly with lake level, but the average loss is about 150 cfs, more than 90 percent of its total supply. The destination of the seepage loss is not definitely known for any of the lakes. An approximate water budget was computed for stationary level for each lake, by using estimates 'by the writer to supplement the hydrologic data available. The three lake waters are dilute. Crater Lake contains about 80 ppm, (parts per million) of dissolved solids---mostly silica, sodium, and bicarbonate, and lesser amounts of calcium, sulfate, and chloride. Much of the dissolved-solids content of Crater Lake---especially the sulfate and chloride---may be related to fumarole and thermal-spring activity that presumably followed the collapse of Mount Mazama. Although Grater Lake loses an estimated 7,000 tons of its 1.5million-ton salt content each year by leakage, the chemical character of the lake did not change appreciably between 1912 and 1964. East Lake contains 200 ppm of dissolved solids, which includes major proportions of calcium, sodium, bicarbonate, and sulfate, but almost no chloride. The lake apparently receives much of its dissolved solids from subsurface thermal springs. Annual solute loss from East Lake by leakage is about 450 tons, or 3 percent of the lake's 15,000-ton estimated solute content. Davis Lake contains only 48 ppm of dissolved solids, much of which is silica and bicarbonate; chloride is almost completely absent

  1. Seasonal variations in geochemistry of the hyperacidic Ijen Crater Lake, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Sumarti, S.; Sumarti, S.; van Bergen, M. J.; Takano, B.; Sukarnen, S.

    2001-12-01

    Kawah Ijen is a typical crater lake in a tropical climate where there is a balance between the volume of atmospheric precipitation and the level of water in the lake. The crater lake has a regular oval form (600 x 1000 m2), is 180 m deep, and contains about 36 million m3 of turquoise-green colored water (pH ~ 0.2). The water contains extremely high Cl, SO4, F concentrations, the maximum values being about 2,500 mg/kg, 80,000 mg/kg and 1,300 mg/kg respectively. Twenty-four samples of lake water taken during August 1996 (dry season) show most major elements to be homogeneously distributed throughout the lake at this time to a depth of 165 m within a standard deviation of less than 10 %. Homogeneity is most likely due to thorough mixing driven by thermal convection. However, iron and sulphur do not behave in the same way showing variations up to 14 % variation. Monthly monitoring of surface water (1997-2001) shows temporal fluctuations in acidity (pH 0 ~ 0.6) and water level, concentrations of major elements, temperature (20 ~ 45° C). Between 1976-1996, the water level varied by ~ 15 m; and from 1997-2001 by ~ 10 m. The onset of the wet season may coincide with an episodical decrease, a spike, in major element concentrations up to 70 % of their dry season value. This spike occurs annually at the lowest temperature and highest degree of dilution, indicates of the influence of rainfall. However, volcanic gases entering beneath the lake bottom may have added to these temporal changes in the lake especially during phreatic eruptions. Shallow earthquake records do not indicate correlations between seismic activity and chemical changes in the lake. Temporal variations of lake surface temperature show good agreement with major element variations in surface water. Crater lake surface water collected at three points on August 1996, March 2001, May 2001 revealed that the surface water was homogenous in the dry and rainy season within a standard deviation below 7 %. The

  2. An Igneous Origin for Features of a Candidate Crater-Lake System in Western Memnonia, Mars

    NASA Technical Reports Server (NTRS)

    Leverington, D. W.; Maxwell, T. A.

    2004-01-01

    The association of channels, inner terraces, and delta-like features with Martian impact craters has previously been interpreted as evidence in favor of the past existence of crater lakes on Mars. However, examination of a candidate crater-lake system in western Memnonia suggests instead that its features may have formed through igneous processes involving the flow and ponding of lava. Accumulations of material in craters and other topographic lows throughout much of the study region have characteristics consistent with those of volcanic deposits, and terraces found along the inner flanks of some of these craters are interpreted as having formed through drainage or subsidence of volcanic materials. Channels previously identified as inlets and outlets of the crater-lake system are interpreted instead as volcanic rilles. These results challenge previous interpretations of terrace and channel features in the study region and suggest that candidate crater lakes located elsewhere should be reexamined.

  3. Hydrochemical dynamics of the “lake spring” system in the crater of El Chichón volcano (Chiapas, Mexico)

    NASA Astrophysics Data System (ADS)

    Rouwet, D.; Taran, Y.; Inguaggiato, S.; Varley, N.; Santiago Santiago, J. A.

    2008-12-01

    El Chichón volcano (Chiapas, Mexico) erupted violently in March-April 1982, breaching through the former volcano-hydrothermal system. Since then, the 1982 crater has hosted a shallow (1-3.3 m, acidic (pH ˜ 2.2) and warm (˜ 30 °C) crater lake with a strongly varying chemistry (Cl/SO 4 = 0-79 molar ratio). The changes in crater lake chemistry and volume are not systematically related to the seasonal variation of rainfall, but rather to the activity of near-neutral geyser-like springs in the crater (Soap Pool). These Soap Pool springs are the only sources of Cl for the lake. Their geyser-like behaviour with a long-term (months to years) periodicity is due to a specific geometry of the shallow boiling aquifer beneath the lake, which is the remnant of the 1983 Cl-rich (24,000 mg/l) crater lake water. The Soap Pool springs decreased in Cl content over time. The zero-time extrapolation (1982, year of the eruption) approaches the Cl content in the initial crater lake, meanwhile the extrapolation towards the future indicates a zero-Cl content by 2009 ± 1. This particular situation offers the opportunity to calculate mass balance and Cl budget to quantify the lake-spring system in the El Chichón crater. These calculations show that the water balance without the input of SP springs is negative, implying that the lake should disappear during the dry season. The isotopic composition of lake waters (δD and δ 18O) coincide with this crater lake-SP dynamics, reflecting evaporation processes and mixing with SP geyser and meteoric water. Future dome growth, not observed yet in the post-1982 El Chichón crater, may be anticipated by changes in lake chemistry and dynamics.

  4. Ultraviolet radiation and bio-optics in Crater Lake, Oregon

    USGS Publications Warehouse

    Hargreaves, B.R.; Girdner, S.F.; Buktenica, M.W.; Collier, R.W.; Urbach, E.; Larson, G.L.

    2007-01-01

    Crater Lake, Oregon, is a mid-latitude caldera lake famous for its depth (594 m) and blue color. Recent underwater spectral measurements of solar radiation (300-800 nm) support earlier observations of unusual transparency and extend these to UV-B wavelengths. New data suggest that penetration of solar UVR into Crater Lake has a significant ecological impact. Evidence includes a correlation between water column chlorophyll-a and stratospheric ozone since 1984, the scarcity of organisms in the upper water column, and apparent UV screening pigments in phytoplankton that vary with depth. The lowest UV-B diffuse attenuation coefficients (K d,320) were similar to those reported for the clearest natural waters elsewhere, and were lower than estimates for pure water published in 1981. Optical proxies for UVR attenuation were correlated with chlorophyll-a concentration (0-30 m) during typical dry summer months from 1984 to 2002. Using all proxies and measurements of UV transparency, decadal and longer cycles were apparent but no long-term trend since the first optical measurement in 1896. ?? 2007 Springer Science+Business Media B.V.

  5. Gas bursts from cameroon crater lakes: a new natural hazard.

    PubMed

    Sigurdsson, H

    1988-06-01

    Gas bursts from tropical crater lakes constitute a hitherto unrecognized natural hazard, which claimed 37 lives around Lake Monoun in 1984 and 1,746 lives in 1986 around Lake Nyos in Cameroon, west Africa. Studies of these events indicate that the lethal gas clouds were dominantly CO(2) which exsolved catastrophically from deep waters of the lakes, producing in the case of Lake Nyos a gas cloud of 1.94 times 10(6) tons CO(2) . Carbon-isotope data indicate a magmatic source of the carbon dioxide, but the geochemistry of deep water and gases does not support a sudden injection of volcanic gas from a deep source into the lakes. Rather, it is proposed that the gas bursts were preceded by gradual build-up of dissolved bicarbonate in deep waters, where anoxic conditions in enclosed and stagnant basins led to low pH and pCO(2) close to saturation. Steady input from the Earth's mantle to submerged mofettes or CO(2) -rich soda springs within the lakes is most likely the primary source of carbon dioxide. Lethal effects of the gas bursts are almost entirely due to CO(2) -induced asphyxia. A small percentage of victims awoke from coma one or two days after the event, but most died. Unusual skin lesions on about 5% of victims arose from the comatose state. It is shown that the mass of gas required to account for the lethal effects and observed gas clouds is an order of magnitude less than the potential gas yield from the lakes. In view of the lethal gas bursts from the small Cameroon lakes, the potential hazard of future gas bursts from other much larger density-stratified equatorial lakes must be seriously considered, particularly in Lake Kivu in east Africa, where methane and carbon dioxide gas content is higher by two to four orders of magnitude than that of the Cameroon lakes. A gas burst from Lake Kivu would form a carbon dioxide cloud up to 340 km(3) in volume and expansion of the exsolving gas from deep water to atmospheric pressure would correspond to an energy release

  6. Gas bursts from cameroon crater lakes: a new natural hazard.

    PubMed

    Sigurdsson, H

    1988-06-01

    Gas bursts from tropical crater lakes constitute a hitherto unrecognized natural hazard, which claimed 37 lives around Lake Monoun in 1984 and 1,746 lives in 1986 around Lake Nyos in Cameroon, west Africa. Studies of these events indicate that the lethal gas clouds were dominantly CO(2) which exsolved catastrophically from deep waters of the lakes, producing in the case of Lake Nyos a gas cloud of 1.94 times 10(6) tons CO(2) . Carbon-isotope data indicate a magmatic source of the carbon dioxide, but the geochemistry of deep water and gases does not support a sudden injection of volcanic gas from a deep source into the lakes. Rather, it is proposed that the gas bursts were preceded by gradual build-up of dissolved bicarbonate in deep waters, where anoxic conditions in enclosed and stagnant basins led to low pH and pCO(2) close to saturation. Steady input from the Earth's mantle to submerged mofettes or CO(2) -rich soda springs within the lakes is most likely the primary source of carbon dioxide. Lethal effects of the gas bursts are almost entirely due to CO(2) -induced asphyxia. A small percentage of victims awoke from coma one or two days after the event, but most died. Unusual skin lesions on about 5% of victims arose from the comatose state. It is shown that the mass of gas required to account for the lethal effects and observed gas clouds is an order of magnitude less than the potential gas yield from the lakes. In view of the lethal gas bursts from the small Cameroon lakes, the potential hazard of future gas bursts from other much larger density-stratified equatorial lakes must be seriously considered, particularly in Lake Kivu in east Africa, where methane and carbon dioxide gas content is higher by two to four orders of magnitude than that of the Cameroon lakes. A gas burst from Lake Kivu would form a carbon dioxide cloud up to 340 km(3) in volume and expansion of the exsolving gas from deep water to atmospheric pressure would correspond to an energy release

  7. Morphology, volcanism, and mass wasting in Crater Lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Gardner, J.V.; Mayer, L.A.; Buktenica, M.W.; Dartnell, P.; Ramsey, D.W.; Robinson, J.E.

    2002-01-01

    Crater Lake was surveyed nearly to its shoreline by high-resolution multibeam echo sounding in order to define its geologic history and provide an accurate base map for research and monitoring surveys. The bathymetry and acoustic backscatter reveal the character of landforms and lead to a chronology for the concurrent filling of the lake and volcanism within the ca. 7700 calibrated yr B.P. caldera. The andesitic Wizard Island and central-plattform volcanoes are composed of sequences of lava deltas that record former lake levels and demonstrate simultaneous activity at the two vents. Wizard Island eruptions ceased when the lake was ~80 m lower than at present. Lava streams from prominent channels on the surface of the central platform descended to feed extensive subaqueous flow fields on the caldera floor. The Wizard Island and central-platform volcanoes, andesitic Merriam Cone, and a newly discovered probable lava flow on the eastern floor of the lake apparently date from within a few hundred years of caldera collapse, whereas a small rhydacite dome was emplaced on the flank of Wizard Island at ca. 4800 cal. yr B.P. Bedrock outcrops on the submerged caldera walls are shown in detail and, in some cases, can be correlated with exposed geologic units of Mount Mazama. Fragmental debris making up the walls elsewhere consists of narrow talus cones forming a dendritic pattern that leads to fewer, wider ridges downslope. Hummocky topography and scattered blocks up to ~280 m long below many of the embayments in the caldera wall mark debris-avalanche deposits that probably formed in single events and commonly are affected by secondary failures. The flat-floored, deep basins contain relatively fine-grained sediment transported from the debris aprons by sheet-flow turbidity currents. Crater Lake apparently filled rapidly (ca. 400-750 yr) until reaching a permeable layer above glaciated lava identified by the new survey in the northeast caldera wall at ~1845 m elevation

  8. Distribution and abundance of zooplankton populations in Crater Lake, Oregon

    USGS Publications Warehouse

    Larson, G.L.; McIntire, C.D.; Buktenica, M.W.; Girdner, S.F.; Truitt, R.E.

    2007-01-01

    The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both. ?? 2007 Springer Science+Business Media B.V.

  9. Remarkable geochemical changes and degassing at Voui crater lake, Ambae volcano, Vanuatu

    NASA Astrophysics Data System (ADS)

    Bani, Philipson; Oppenheimer, Clive; Varekamp, Johan C.; Quinou, Thomas; Lardy, Michel; Carn, Simon

    2009-12-01

    Ambae (also known as Aoba), is a 38 × 16 km 2 lozenge-shaped island volcano with a coastal population of around 10 000. At the summit of the volcano is lake Voui — one of the largest active crater lakes worldwide, with 40 × 10 6 m 3 of acidic water perched 1400 m a.s.l. After more than 300 years of dormancy, Ambae volcano reawakened with phreatic eruptions through Voui in 1995, and culminating in a series of surtseyan eruptions in 2005, followed by a rapid and spectacular colour change of the lake from light blue to red in 2006. Integrating lake water chemistry with new measurements of SO 2 emissions from the volcano during the 2005-2006 eruptive period helps to explain the unusual and spectacular volcanic activity of Ambae — initially, a degassed magma approached the lake bed and triggered the surtseyan eruption. Depressurization of the conduit facilitated ascent of volatile-rich magma from the deeper plumbing system. The construction of a cone during eruption and the high degassing destabilised the equilibrium of lake stratification leading to a limnic event and subsequently the spectacular colour change.

  10. Comparative physiographic diagrams of Mount St. Helens, Washington, and Crater Lake, Oregon

    USGS Publications Warehouse

    Alpha, Tau Rho; Morley, Jim M.

    1983-01-01

    These physiographic diagrams provide a visual comparison of two Cascade Range volcanoes which have had their tops destroyed in different ways -- Mount St. Helens in 1980, Mount Mazama (whose site is now occupied by Crater Lake) about 6,800 years ago. Both volcanoes are viewed from the north from 30 degrees above the horizon, with no vertical exaggeration. The ground area portrayed in each diagram is equal; the south edge of the Mount St. Helens drawing is lower than that of Crater Lake drawing because elevations drop away toward the south, whereas elevations are more constant at the north and south edges of the Crater Lake diagram. 

  11. Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars.

    PubMed

    Grotzinger, J P; Gupta, S; Malin, M C; Rubin, D M; Schieber, J; Siebach, K; Sumner, D Y; Stack, K M; Vasavada, A R; Arvidson, R E; Calef, F; Edgar, L; Fischer, W F; Grant, J A; Griffes, J; Kah, L C; Lamb, M P; Lewis, K W; Mangold, N; Minitti, M E; Palucis, M; Rice, M; Williams, R M E; Yingst, R A; Blake, D; Blaney, D; Conrad, P; Crisp, J; Dietrich, W E; Dromart, G; Edgett, K S; Ewing, R C; Gellert, R; Hurowitz, J A; Kocurek, G; Mahaffy, P; McBride, M J; McLennan, S M; Mischna, M; Ming, D; Milliken, R; Newsom, H; Oehler, D; Parker, T J; Vaniman, D; Wiens, R C; Wilson, S A

    2015-10-01

    The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).

  12. Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars

    USGS Publications Warehouse

    Grotzinger, J.P.; Gupta, S.; Malin, M.C.; Rubin, D.M.; Schieber, J.; Siebach, K.; Sumner, D.Y.; Stack, K.M.; Vasavada, A.R.; Arvidson, R.E.; Calef, F.; Edgar, Lauren; Fischer, W.F.; Grant, J.A.; Griffes, J.L.; Kah, L.C.; Lamb, M.P.; Lewis, K.W.; Mangold, N.; Minitti, M.E.; Palucis, M.C.; Rice, M.; Williams, R.M.E.; Yingst, R.A.; Blake, D.; Blaney, D.; Conrad, P.; Crisp, J.A.; Dietrich, W.E.; Dromart, G.; Edgett, K.S.; Ewing, R.C.; Gellert, R.; Hurowitz, J.A.; Kocurek, G.; Mahaffy, P.G.; McBride, M.J.; McLennan, S.M.; Mischna, M.A.; Ming, D.; Milliken, R.E.; Newsom, H.; Oehler, D.; Parker, T.J.; Vaniman, D.; Wiens, R.C.; Wilson, S.A.

    2015-01-01

    The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).

  13. Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars.

    PubMed

    Grotzinger, J P; Gupta, S; Malin, M C; Rubin, D M; Schieber, J; Siebach, K; Sumner, D Y; Stack, K M; Vasavada, A R; Arvidson, R E; Calef, F; Edgar, L; Fischer, W F; Grant, J A; Griffes, J; Kah, L C; Lamb, M P; Lewis, K W; Mangold, N; Minitti, M E; Palucis, M; Rice, M; Williams, R M E; Yingst, R A; Blake, D; Blaney, D; Conrad, P; Crisp, J; Dietrich, W E; Dromart, G; Edgett, K S; Ewing, R C; Gellert, R; Hurowitz, J A; Kocurek, G; Mahaffy, P; McBride, M J; McLennan, S M; Mischna, M; Ming, D; Milliken, R; Newsom, H; Oehler, D; Parker, T J; Vaniman, D; Wiens, R C; Wilson, S A

    2015-10-01

    The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp). PMID:26450214

  14. Convective heat discharge of Wood River group of springs in the vicinity of Crater Lake, Oregon

    USGS Publications Warehouse

    Nathenson, Manuel; Mariner, Robert H.; Thompson, J. Michael

    1994-01-01

    Data sets for spring and stream chemistry are combined to estimate convective heat discharge and discharge anomalous amounts of sodium and chloride for the Wood River group of springs south of Crater Lake. The best estimate of heat discharge is 87 MWt based on chloride inventory; this value is 3-5 times the heat input to Crater Lake itself. Anomalous discharges of sodium and chloride are also larger that into Crater Lake. Difference between the chemical and thermal characteristics of the discharge into Crater Lake and those from the Wood River group of springs suggest that the heat sources for the two systems may be different, although both ultimately related to the volcanic system.

  15. El Chichón crater lake dynamic based on continuous physical data and mass-heat budget

    NASA Astrophysics Data System (ADS)

    Peiffer, L.; Taran, Y.

    2011-12-01

    The March-April 1982 Plinian eruption of El Chichón volcano destroyed the summit domes system and created a new 200 m deep crater. Since then, a shallow lake (~3 m) with acidic pH (~2.3), and temperature around 30°C appeared in the crater. This lake has never disappeared until now although its volume has suffered important variations from 40,000 m3 to 160,000 m3. Chemical composition of the lake is also highly variable (Cl/SO4 = 0-79 molar ratio), alternating between acid-sulfate and acid-chloride-sulfate composition. These variations can occur very fast within few weeks and are not directly correlated with precipitation. Due to its shallow depth and small volume, El Chichón crater lake is probably one of the most dynamic crater lake on earth. These rapid changes in chemistry and volume reflect the dynamic of one group of geyser-type springs ('Soap Pools springs, SP') located offshore and the input of hydrothermal steam underneath the crater. The SP springs discharge sporadically to the lake neutral waters with Cl content currently around 3000 mg/l, while the condensed steam feeds the lake with Cl-free and SO4-rich acid water. In this study, we present for the first time continuous physical data of the crater lake (temperature, depth, meteoric precipitation, wind velocity, solar radiation, air humidity). These data were registered by a meteorological station and two dataloggers installed inside and outside the lake. Using a mass and heat budget model constrained with these data, we were able to estimate the flux of 'hydrothermal' fluid entering the lake through the sub-lacustrian fumaroles and SP springs. Tracing the variations of the input flux in time can be help to understand the dynamic of the 'crater lake-SP springs-fumaroles' system but also can provide an efficient way of monitoring the volcanic activity. During the observation period, the mean mass flux entering the lake (Min) was respectively of 12 ± 2 kg/s, corresponding to a total heat flux (Ein) of

  16. Lonar Lake, India: An impact Crater in basalt

    USGS Publications Warehouse

    Fredriksson, K.; Dube, A.; Milton, D.J.; Balasundaram, M.S.

    1973-01-01

    Discovery of shock-metamorphosed material establishes the impact origin of Lonar Crater. Coarse breccia with shatter coning and microbreccia with moderately shocked fragments containing maskelynite were found in drill holes through the crater floor. Trenches on the rim yield strongly shocked fragments in which plagioclase has melted and vesiculated, and bombs and spherules of homogeneous rock melt. As the only known terrestrial impact crater in basalt, Lonar Crater provides unique opportunities for comparison with lunar craters. In particular, microbreccias and glass spherules from Lonar Crater have close analogs among the Apollo specimens.

  17. Lonar lake, India: an impact crater in basalt.

    PubMed

    Fredriksson, K; Dube, A; Milton, D J; Balasundaram, M S

    1973-05-25

    Discovery of shock-metamorphosed material establishes the impact origin of Lonar Crater. Coarse breccia with shatter coning and microbreccia with moderately shocked fragments containing maskelynite were found in drill holes through the crater floor. Trenches on the rim yield strongly shocked fragments in which plagioclase has melted and vesiculated, and bombs and spherules of homogeneous rock melt. As the only known terrestrial impact crater in basalt, Lonar Crater provides unique opportunities for comparison with lunar craters. In particular, microbreccias and glass spherules from Lonar Crater have close analogs among the Apollo specimens.

  18. A symbiotic view of the origin of life at hydrothermal impact crater-lakes.

    PubMed

    Chatterjee, Sankar

    2016-07-27

    Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. The theory suffers from the 'concentration problem' of cosmic and terrestrial biomolecules because of the vastness of the Eoarchean global ocean. An attractive alternative site would be highly sequestered, small, hydrothermal crater-lakes that might have cradled life on early Earth. A new symbiotic model for the origin of life at hydrothermal crater-lakes is proposed here. Meteoritic impacts on the Eoarchean crust at the tail end of the Heavy Bombardment period might have played important roles in the origin of life. Impacts and collisions that created hydrothermal crater lakes on the Eoarchean crust inadvertently became the perfect crucibles for prebiotic chemistry with building blocks of life, which ultimately led to the first organisms by prebiotic synthesis. In this scenario, life arose through four hierarchical stages of increasing molecular complexity in multiple niches of crater basins. In the cosmic stage (≥4.6 Ga), the building blocks of life had their beginnings in the interstellar space during the explosion of a nearby star. Both comets and carbonaceous chondrites delivered building blocks of life and ice to early Earth, which were accumulated in hydrothermal impact crater-lakes. In the geologic stage (∼4 Ga), crater basins contained an assortment of cosmic and terrestrial organic compounds, powered by hydrothermal, solar, tidal, and chemical energies, which drove the prebiotic synthesis. At the water surface, self-assembled primitive lipid membranes floated as a thick oil slick. Archean Greenstone belts in Greenland, Australia, and South Africa possibly represent the relics of these Archean craters, where the oldest fossils of thermophilic life (∼3.5 Ga) have been detected. In the chemical stage, monomers such as nucleotides and amino acids were selected from random assemblies of the prebiotic soup; they were

  19. A symbiotic view of the origin of life at hydrothermal impact crater-lakes.

    PubMed

    Chatterjee, Sankar

    2016-07-27

    Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. The theory suffers from the 'concentration problem' of cosmic and terrestrial biomolecules because of the vastness of the Eoarchean global ocean. An attractive alternative site would be highly sequestered, small, hydrothermal crater-lakes that might have cradled life on early Earth. A new symbiotic model for the origin of life at hydrothermal crater-lakes is proposed here. Meteoritic impacts on the Eoarchean crust at the tail end of the Heavy Bombardment period might have played important roles in the origin of life. Impacts and collisions that created hydrothermal crater lakes on the Eoarchean crust inadvertently became the perfect crucibles for prebiotic chemistry with building blocks of life, which ultimately led to the first organisms by prebiotic synthesis. In this scenario, life arose through four hierarchical stages of increasing molecular complexity in multiple niches of crater basins. In the cosmic stage (≥4.6 Ga), the building blocks of life had their beginnings in the interstellar space during the explosion of a nearby star. Both comets and carbonaceous chondrites delivered building blocks of life and ice to early Earth, which were accumulated in hydrothermal impact crater-lakes. In the geologic stage (∼4 Ga), crater basins contained an assortment of cosmic and terrestrial organic compounds, powered by hydrothermal, solar, tidal, and chemical energies, which drove the prebiotic synthesis. At the water surface, self-assembled primitive lipid membranes floated as a thick oil slick. Archean Greenstone belts in Greenland, Australia, and South Africa possibly represent the relics of these Archean craters, where the oldest fossils of thermophilic life (∼3.5 Ga) have been detected. In the chemical stage, monomers such as nucleotides and amino acids were selected from random assemblies of the prebiotic soup; they were

  20. Analysis of the Paleoenvironment of Gale Crater on Mars: Using Ephemeral Lakes in Western Australia as Analogs to the Mineral Assemblages of Gale Crater

    NASA Astrophysics Data System (ADS)

    Cocks, C.; Baldridge, A. M.; Thomson, B. J.

    2014-12-01

    Aluminum and Fe/Mg-phyllosilicates, as well as sulfates, are abundant in the layered sediments of the central mound of Gale Crater on Mars. Each of these mineral types are useful indicators of depositional conditions regarding pH, where Fe/Mg-phyllosilicates form in higher pH waters, while Al-phyllosilicates and sulfates form in more acidic waters. A general succession from higher pH aquatic environments to lower pH environments is evident during the Noachian and early Hesperian (3.6~3.8 Ga). However, substantial interbedding of these mineral groups is also observed at Gale, indicating pH boundaries that existed contemporaneously at the time of deposition. This is consistent with mineral distributions that are observed in ephemeral lakes on Earth, making them useful as analogs to the geochemistry of Gale Crater. This study will analyze the surficial mineral depositional patterns at Lake Gilmore, WA, to better understand how pH gradients are represented in contemporaneous sediment deposits. This will be performed by identifying minerals based on their unique reflectance signatures in the visible to near-infrared range (0.5-2.5 mm). Reflectance data collected by the HyMap™ hyperspectral scanner will be analyzed using the ENVI software to map the predominant minerals present on the lakebed surface. We expect to see minerals associated with a pH gradient that is related to lake depth, with Fe and alkali earth phyllosilicates representing deeper, less acidic waters, and aluminous phyllosilicates and sulfates representing near surface waters that are more acidic. This is potentially due to the circulation of upwelling groundwaters, or the change in chemistry may have arisen due to microbial activity, an intriguing possibility that would have significant implications for evidence of past microbial life on the Martian surface and would provide a more detailed picture of the paleoenvironment at Gale Crater.

  1. Digital Data for Volcano Hazards in the Crater Lake Region, Oregon

    USGS Publications Warehouse

    Schilling, S.P.; Doelger, S.; Bacon, C.R.; Mastin, L.G.; Scott, K.E.; Nathenson, M.

    2008-01-01

    Crater Lake lies in a basin, or caldera, formed by collapse of the Cascade volcano known as Mount Mazama during a violent, climactic eruption about 7,700 years ago. This event dramatically changed the character of the volcano so that many potential types of future events have no precedent there. This potentially active volcanic center is contained within Crater Lake National Park, visited by 500,000 people per year, and is adjacent to the main transportation corridor east of the Cascade Range. Because a lake is now present within the most likely site of future volcanic activity, many of the hazards at Crater Lake are different from those at most other Cascade volcanoes. Also significant are many faults near Crater Lake that clearly have been active in the recent past. These faults, and historic seismicity, indicate that damaging earthquakes can occur there in the future. The USGS Open-File Report 97-487 (Bacon and others, 1997) describes the various types of volcano and earthquake hazards in the Crater Lake area, estimates of the likelihood of future events, recommendations for mitigation, and a map of hazard zones. The geographic information system (GIS) volcano hazard data layers used to produce the Crater Lake earthquake and volcano hazard map in USGS Open-File Report 97-487 are included in this data set. USGS scientists created one GIS data layer, c_faults, that delineates these faults and one layer, cballs, that depicts the downthrown side of the faults. Additional GIS layers chazline, chaz, and chazpoly were created to show 1)the extent of pumiceous pyroclastic-flow deposits of the caldera forming Mount Mazama eruption, 2)silicic and mafic vents in the Crater Lake region, and 3)the proximal hazard zone around the caldera rim, respectively.

  2. Seismic Investigation and Numerical Modeling of the Lake Bosumtwi Impact Crater

    NASA Astrophysics Data System (ADS)

    Karp, T.; Artemieva, N. A.; Milkereit, B.

    2003-02-01

    The Lake Bosumtwi impact crater, Ghana, (age 1.07 Ma, diameter 10.5 km) is one of the youngest and best-preserved complex terrestrial impact structures. It was excavated from hard crystalline target rock and is the source of the Ivory Coast tektite strewn field. It is almost entirely filled by the Lake Bosumtwi.

  3. Acid Sulfate Alteration in Gusev Crater, Mars

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Ming, D. W.; Catalano, J. G.

    2016-01-01

    The Mars Exploration Rover (MER) Spirit landed on the Gusev Crater plains west of the Columbia Hills in January, 2004, during the Martian summer (sol 0; sol = 1 Martian day = 24 hr 40 min). Spirit explored the Columbia Hills of Gusev Crater in the vicinity of Home Plate at the onset on its second winter (sol approximately 900) until the onset of its fourth winter (sol approximately 2170). At that time, Spirit became mired in a deposit of fined-grained and sulfate-rich soil with dust-covered solar panels and unfavorable pointing of the solar arrays toward the sun. Spirit has not communicated with the Earth since sol 2210 (January, 2011). Like its twin rover Opportunity, which landed on the opposite side of Mars at Meridiani Planum, Spirit has an Alpha Particle X-Ray Spectrometer (APXS) instrument for chemical analyses and a Moessbauer spectrometer (MB) for measurement of iron redox state, mineralogical speciation, and quantitative distribution among oxidation (Fe(3+)/sigma Fe) and coordination (octahedral versus tetrahedral) states and mineralogical speciation (e.g., olivine, pyroxene, ilmenite, carbonate, and sulfate). The concentration of SO3 in Gusev rocks and soils varies from approximately 1 to approximately 34 wt%. Because the APXS instrument does not detect low atomic number elements (e.g., H and C), major-element oxide concentrations are normalized to sum to 100 wt%, i.e., contributions of H2O, CO2, NO2, etc. to the bulk composition care not considered. The majority of Gusev samples have approximately 6 plus or minus 5 wt% SO3, but there is a group of samples with high SO3 concentrations (approximately 30 wt%) and high total iron concentrations (approximately 20 wt%). There is also a group with low total Fe and SO3 concentrations that is also characterized by high SiO2 concentrations (greater than 70 wt%). The trend labeled "Basaltic Soil" is interpreted as mixtures in variable proportions between unaltered igneous material and oxidized and SO3-rich basaltic

  4. Water Quality and optical properties of Crater Lake, Oregon

    USGS Publications Warehouse

    Larson, Gary L.; Hoffman, Robert L.; McIntire, C.D.; Buktenica, M.W.; Girdner, Scott

    2007-01-01

    We examine observations of key limnological properties (primarily temperature, salinity, and dissolved oxygen), measured over a 14-year period in Crater Lake, Oregon, and discuss variability in the hypolimnion on time scales of days to a decade. During some years (e.g., 1994a??1995), higher-than-average wintertime deep convection and ventilation led to the removal of significant amounts of heat and salt from the hypolimnion, while dissolved oxygen concentrations increase. In other years, such as the winter of 1996a??1997, heat and salt concentrations increase throughout the year and dissolved oxygen levels drop, indicating conditions were dominated by the background geothermal inputs and dissolved oxygen consumption by bacteria (i.e., minimal deep convection). Over the entire 14 year period, no statistically significant trend was observed in the annual hypolimnetic heat and salt content. Measurements from several thermistors moored in the hypolimnion provide new insight into the time and space scales of the deep convection events. For some events, cool water intrusions are observed sequentially, from shallower depths to deeper depths, suggesting vertical mixing or advection from above. For other events, the cooling is observed first at the deepest sensors, suggesting a thin, cold water pulse that flows along the bottom and mixes more slowly upwards into the basin. In both cases, the source waters must originate from the epilimnion. Conditions during a strong ventilation year (1994a??1995) and a weak ventilation year (1996a??1997) were compared. The results suggest the major difference between these 2 years was the evolution of the stratification in the epilimnion during the first few weeks of reverse stratification such that thermobaric instabilities were easier to form during 1995 thana?#1997. Thus, the details of surface cooling and wind-driven mixing during the early stages ofa?#reverse stratification may determine the neta?#amount of ventilation possible during

  5. Deglacial and postglacial evolution of the Pingualuit Crater Lake basin, northern Québec (Canada)

    NASA Astrophysics Data System (ADS)

    Desiage, Pierre-Arnaud; Lajeunesse, Patrick; St-Onge, Guillaume; Normandeau, Alexandre; Ledoux, Grégoire; Guyard, Hervé; Pienitz, Reinhard

    2015-11-01

    The Pingualuit Crater, located in the Ungava Peninsula (northern Québec, Canada) is a 1.4-Ma-old impact crater hosting a ~ 245-m-deep lake. The lake has a great potential to preserve unique paleoclimatic and paleoecological sedimentary records of the last glacial/interglacial cycles in the terrestrial Canadian Arctic. In order to investigate the stratigraphy in the lake and the late Quaternary glacial history of the Pingualuit Crater, this study compiles data from three expeditions carried out in May 2007 (~ 9-m-long sediment core), in August 2010 (~ 50 km of seismic lines), and in September 2012 (high-resolution terrestrial LiDAR topography of the inner slopes). Despite the weak penetration (~ 10 m) of the 3.5-kHz subbottom profiling caused by the presence of boulders in the sedimentary column, seismic data coupled with the stratigraphy established from the sediment core enabled the identification of two glaciolacustrine units deposited during the final stages of the Laurentide Ice Sheet (LIS) retreat in the crater. Two episodes of postglacial mass wasting events were also identified on the slopes and in the deep basin of the crater. The high-resolution topography of the internal slopes of the crater generated from the LiDAR data permitted the confirmation of a paleolake level at 545 m and determination of the elevation of drainage outlets. Together with the mapping of glacial and deglacial landforms from air photographs, the LiDAR data allowed the development of a new deglaciation and drainage scenario for the Pingualuit Crater Lake and surrounding area. The model proposes three main phases of lake drainage, based on the activation of seven outlets following the retreat of the LIS front toward the southwest. Finally, as opposed to other high-latitude crater lake basins such as Lake El'gygytgyn or Laguna Potrok Aike where high-resolution paleoclimatic records were obtained owing to high sediment accumulation rates, the seismic data from the Pingualuit Crater Lake

  6. Vertical distribution of a deep-water moss and associated epiphytes in Crater Lake, Oregon

    USGS Publications Warehouse

    McIntire, C.D.; Phinney, H.K.; Larson, Gary L.; Buktenica, M.W.

    1994-01-01

    A one-person submersible was used to examine the vertical distribution of the deep-water moss Drepanocladus aduncus (Hedw.) Warnst in Crater Lake (Oregon). Living specimens were found attached to sediment and rocks at depths between 25 m and 140 m. Dense beds of the moss were observed at depths between 30 m and 80 m, a region that corresponded roughly to the zone of maximum primary production by phytoplankton. The moss population supported a diverse assemblage of epiphytic algae, of which the most abundant genera included Cladophora,Oedogonium, Rhizoclonium, Tribonema, Vaucheria, and the diatoms Cocconeis, Cymbella, Epithemia, Fragilaria, Gomphonema, Melosira, Navicula, and Synedra. Chemical and physical data supported the hypothesis that the lower limit of distribution of the moss is determined by light limitation, whereas the upper limit is related to the availability of nutrients, particularly nitrate-nitrogen and trace elements. Deep-water videotapes of the moss population indicated that D. aduncus with its epiphytic algae was abundant enough in regions associated with the metalimnion and upper hypolimnion to have a potential influence on the nutrient dynamics of the Crater Lake ecosystem. Although the maximum depth at which living bryophytes occur in Crater Lake is similar to that found for Lake Tahoe, conditions in Lake Tahoe allow the growth and survival of a much more diverse assemblage of bryophytes and charophytes than is present in Crater Lake.

  7. Geophysical Signature of the Lake Bosumtwi Impact Crater from Pre-drilling Site Surveys

    NASA Astrophysics Data System (ADS)

    Banour, S.; Pohl, J.; Menyeh, A.; Milkereit, B.; Boadu, F.

    2006-12-01

    The Bosumtwi impact crater located near Kumasi, Ghana was formed by a meteorite impact about one million years ago and has a diameter of about 10.5 km. Geophysical investigations involving gravity and magnetic measurements were carried out at the Bosumtwi crater to determine the geophysical signature of the crater with the aim of understanding the impact process. Gravity data was acquired on land at 163 locations around the crater area, as well as on the shore of the lake. The separation between the gravity stations was 500 m for profiles which ran radially toward the lake, and 700 1000 m along roads and footpaths which ran parallel to the shore. In addition, marine gravity and magnetic surveys were carried out along 14 north-south and 15 east- west profiles on the lake with a line spacing of 800 m using a Garmin 235 Echo Sounder/GPS as a navigational tool. Results from gravity modelling showed that the gravity signature of the crater is characterized by a negative Bouguer anomaly with an amplitude roughly equal to 18 mgal. The results also indicated a central uplift at 250 m depth below the lake, thus confirming it as a complex impact crater. Magnetic modelling yielded a model for the causative body, which is located north of the central uplift. The model has a magnetic susceptibility of 0.03 SI and extends from 200 to 610 m depth below the lake surface. The causative body has been interpreted as magnetized bodies consisting of thin sheets of suevitic impact formations. These results serve as a contribution to the understanding of the impact process of this young crater.

  8. Rapid sympatric ecological differentiation of crater lake cichlid fishes within historic times

    PubMed Central

    2010-01-01

    Background After a volcano erupts, a lake may form in the cooled crater and become an isolated aquatic ecosystem. This makes fishes in crater lakes informative for understanding sympatric evolution and ecological diversification in barren environments. From a geological and limnological perspective, such research offers insight about the process of crater lake ecosystem establishment and speciation. In the present study we use genetic and coalescence approaches to infer the colonization history of Midas cichlid fishes (Amphilophus cf. citrinellus) that inhabit a very young crater lake in Nicaragua-the ca. 1800 year-old Lake Apoyeque. This lake holds two sympatric, endemic morphs of Midas cichlid: one with large, hypertrophied lips (~20% of the total population) and another with thin lips. Here we test the associated ecological, morphological and genetic diversification of these two morphs and their potential to represent incipient speciation. Results Gene coalescence analyses [11 microsatellite loci and mitochondrial DNA (mtDNA) sequences] suggest that crater lake Apoyeque was colonized in a single event from the large neighbouring great lake Managua only about 100 years ago. This founding in historic times is also reflected in the extremely low nuclear and mitochondrial genetic diversity in Apoyeque. We found that sympatric adult thin- and thick-lipped fishes occupy distinct ecological trophic niches. Diet, body shape, head width, pharyngeal jaw size and shape and stable isotope values all differ significantly between the two lip-morphs. The eco-morphological features pharyngeal jaw shape, body shape, stomach contents and stable isotopes (δ15N) all show a bimodal distribution of traits, which is compatible with the expectations of an initial stage of ecological speciation under disruptive selection. Genetic differentiation between the thin- and thick-lipped population is weak at mtDNA sequence (FST = 0.018) and absent at nuclear microsatellite loci (FST < 0

  9. Hydrogeochemical monitoring of El Chichón Volcano crater lake, Mexico.

    NASA Astrophysics Data System (ADS)

    Ceniceros, N.; Armienta, M. A.; Ramos, S.; Cruz, O.; Aguayo, A.

    2003-04-01

    The geochemistry of the crater lake of the El Chichón volcano has been studied since 1983. Results have been used to analyze post-eruptive processes and assessing volcanic risk. Chemical analysis has included pH, temperature, principal ions, fluoride, Iron , sulfide, boron and Silica. From 1985, all determinations have been performed at the Analytical Chemistry Laboratory of the Geophysics Institute (National University of Mexico). Such analysis were made following the standard methods, as given in APHA (1989), e.g. UV-visible, emission, and atomic absorption spectroscopy, potentiometric and volumetric techniques.. The El Chichón crater lake water showed an increasing pH from 1983 to 1986 (from 0.56 to 2.33), from then pH has fluctuated around the later value (in August 2002 pH was 1.98). Conductivity showed a high fluctuations with a general decreasing trend, ranging between 83800 uS/cm (1983, Casadevall et al., 1984) and close to 2000 uS/cm (December 1998). Water-type has changed along these years: The Chichon water could be classified as acid, calcium-chloride in 1983; in 1991 changed to Sulfate-mixed and since 1992, it has been mostly of sodium chloride type, except for a few dates when it could be classified as sulfate-mixed or calcic type. Since 1985, cation concentrations produced by environmental rock dissolution decreased in the same manner. A decreasing trend with time was observed also in anions of a potential magmatic origin like sulfate, chloride and fluoride. Molar concentrations of chloride have been mostly greater than sulfate concentrations (up to two orders of magnitude) and have varied without any observed correlation. Oxidation-reduction processes may explain the large sulfate concentration changesSulfate shows large. The geochemical modeling programs (MINTEQA2, PHREEQCE) showed saturation indices close to equilibrium for gypsum and anhydrite suggesting that sulfates also can be derived from other processes such as dissolution

  10. High rate of schistosomiasis in travelers after a brief exposure to the high-altitude Nyinambuga crater lake, Uganda.

    PubMed

    Lachish, Tamar; Tandlich, Moshik; Grossman, Tamar; Schwartz, Eli

    2013-11-01

    Travel-related schistosomiasis is usually associated with prolonged freshwater exposure. Until recently, Uganda's crater lakes were considered schistosomiasis free due to their high-altitude location. We describe an outbreak of acute schistosomiasis after a brief exposure (mean, 22 ± 9.5 minutes) to a high-altitude crater lake.

  11. Shifts in morphology and diet of non-native sticklebacks introduced into Japanese crater lakes

    PubMed Central

    Adachi, Tatsuya; Ishikawa, Asano; Mori, Seiichi; Makino, Wataru; Kume, Manabu; Kawata, Masakado; Kitano, Jun

    2012-01-01

    An increasing number of exotic animals are causing ecological problems. Therefore, for better ecosystem management, it is important to understand how exotic species colonize and adapt to novel environments. The threespine sticklebacks (Gasterosteus aculeatus) can be a good vertebrate model system to explore the ecological and genetic mechanisms of adaptation not only in natural populations, but also in non-native populations. Although morphological changes have been documented in several introduced populations of stickleback, little is known about the dietary changes during colonization into novel environments. Here, we investigated the morphological and dietary changes of exotic threespine stickleback populations introduced into three Japanese crater lakes (Lake Towada, Lake Kussharo, and Lake Shikotsu). Sticklebacks were introduced into the crater lakes likely along with salmonids transplanted for aquaculture. The stickleback population in Lake Kussharo had multiple mitochondrial haplotypes and had larger phenotypic variances than other crater lake stickleback populations that had only one mitochondrial haplotype. Compilation of historical data on the morphology and stomach contents of the Lake Towada stickleback population showed that substantial shifts in body size and stomach contents occurred after colonization. Some of these changes may be related to an outbreak of the Schistocephalus parasite. These results suggest that sticklebacks can change their morphology and trophic ecology when they colonize novel environments. Therefore, extreme care should be taken when salmonids are transported between watersheds for aquaculture and that long-term monitoring of exotic species is essential for ecosystem management. In addition, further genetic studies on phenotypic changes in crater lake sticklebacks would help elucidate the genetic mechanisms underlying the adaptation of exotic fishes to novel environments. PMID:22833786

  12. Shifts in morphology and diet of non-native sticklebacks introduced into Japanese crater lakes.

    PubMed

    Adachi, Tatsuya; Ishikawa, Asano; Mori, Seiichi; Makino, Wataru; Kume, Manabu; Kawata, Masakado; Kitano, Jun

    2012-06-01

    An increasing number of exotic animals are causing ecological problems. Therefore, for better ecosystem management, it is important to understand how exotic species colonize and adapt to novel environments. The threespine sticklebacks (Gasterosteus aculeatus) can be a good vertebrate model system to explore the ecological and genetic mechanisms of adaptation not only in natural populations, but also in non-native populations. Although morphological changes have been documented in several introduced populations of stickleback, little is known about the dietary changes during colonization into novel environments. Here, we investigated the morphological and dietary changes of exotic threespine stickleback populations introduced into three Japanese crater lakes (Lake Towada, Lake Kussharo, and Lake Shikotsu). Sticklebacks were introduced into the crater lakes likely along with salmonids transplanted for aquaculture. The stickleback population in Lake Kussharo had multiple mitochondrial haplotypes and had larger phenotypic variances than other crater lake stickleback populations that had only one mitochondrial haplotype. Compilation of historical data on the morphology and stomach contents of the Lake Towada stickleback population showed that substantial shifts in body size and stomach contents occurred after colonization. Some of these changes may be related to an outbreak of the Schistocephalus parasite. These results suggest that sticklebacks can change their morphology and trophic ecology when they colonize novel environments. Therefore, extreme care should be taken when salmonids are transported between watersheds for aquaculture and that long-term monitoring of exotic species is essential for ecosystem management. In addition, further genetic studies on phenotypic changes in crater lake sticklebacks would help elucidate the genetic mechanisms underlying the adaptation of exotic fishes to novel environments.

  13. Snettisham Hydroelectric Project, Alaska second stage development, Crater lake. Final foundation report. Final report

    SciTech Connect

    Not Available

    1992-09-04

    The important geologic features and methods used to construct the Crater Lake stage of the Snettisham Hydroelectric project, built between 1985 and 1989, are discussed. The project added 31 megawatts of non-polluting, renewable electric power for Juneau, Alaska and the surrounding area. Features of the report include the power tunnel and access adits, penstock excavation, surge shaft, gate shaft and lake top. Construction aspects include the general geology, design features, construction methods, geologic conditions encountered, ground support requirements, grouting, instrumentation and tunnel filling. Foundation conditions for the Crater Lake status were excellent, permitting the power and penstock tunnel and shafts to be constructed essentially unlined. The basic rock type throughout the project is a high-quality, quartz diorite gneiss with randomly spaced, subparallel basalt dikes.... Unlined rock tunnels, Power tunnel, Penstocks, Lake tap, Surge shaft.

  14. Phylogeography, colonization and population history of the Midas cichlid species complex (Amphilophus spp.) in the Nicaraguan crater lakes

    PubMed Central

    2010-01-01

    Background Elucidation of the mechanisms driving speciation requires detailed knowledge about the phylogenetic relationships and phylogeography of the incipient species within their entire ranges as well as their colonization history. The Midas cichlid species complex Amphilophus spp. has been proven to be a powerful model system for the study of ecological specialization, sexual selection and the mechanisms of sympatric speciation. Here we present a comprehensive and integrative phylogeographic analysis of the complete Midas Cichlid species complex in Nicaragua (> 2000 individuals) covering the entire distributional range, using two types of molecular markers (the mitochondrial DNA control region and 15 microsatellites). We investigated the majority of known lake populations of this species complex and reconstructed their colonization history in order to distinguish between alternative speciation scenarios. Results We found that the large lakes contain older and more diverse Midas Cichlid populations, while all crater lakes hold younger and genetically less variable species assemblages. The large lakes appear to have repeatedly acted as source populations for all crater lakes, and our data indicate that faunal exchange among crater lakes is extremely unlikely. Despite their very recent (often only a few thousand years old) and common origin from the two large Nicaraguan lakes, all crater lake Midas Cichlid radiations underwent independent, but parallel, evolution, and comprise distinct genetic units. Indeed several of these crater lakes contain multiple genetically distinct incipient species that most likely arose through sympatric speciation. Several crater lake radiations can be traced back to a single ancestral line, but some appear to have more than one founding lineage. The timing of the colonization(s) of each crater lake differs, although most of them occurred more (probably much more) recently than 20,000 years ago. Conclusion The genetic differentiation

  15. Local variation and parallel evolution: morphological and genetic diversity across a species complex of neotropical crater lake cichlid fishes

    PubMed Central

    Elmer, Kathryn R.; Kusche, Henrik; Lehtonen, Topi K.; Meyer, Axel

    2010-01-01

    The polychromatic and trophically polymorphic Midas cichlid fish species complex (Amphilophus cf. citrinellus) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic diversification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, sampled from six crater lakes (maximally 1.2–23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic diversity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early divergence of each crater lake colonization, followed by intralacustrine diversification and speciation by ecological adaptation and sexual selection. PMID:20439280

  16. Local variation and parallel evolution: morphological and genetic diversity across a species complex of neotropical crater lake cichlid fishes.

    PubMed

    Elmer, Kathryn R; Kusche, Henrik; Lehtonen, Topi K; Meyer, Axel

    2010-06-12

    The polychromatic and trophically polymorphic Midas cichlid fish species complex (Amphilophus cf. citrinellus) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic diversification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, sampled from six crater lakes (maximally 1.2-23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic diversity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early divergence of each crater lake colonization, followed by intralacustrine diversification and speciation by ecological adaptation and sexual selection.

  17. Incipient speciation in sympatric Nicaraguan crater lake cichlid fishes: sexual selection versus ecological diversification.

    PubMed Central

    Wilson, A B; Noack-Kunnmann, K; Meyer, A

    2000-01-01

    The growing body of empirical evidence for sympatric speciation has been complemented by recent theoretical treatments that have identified evolutionary conditions conducive to speciation in sympatry. The Neotropical Midas cichlid (Amphilophus citrinellum) fits both of the key characteristics of these models, with strong assortative mating on the basis of a colour polymorphism coupled with trophic and ecological differentiation derived from a polymorphism in their pharyngeal jaws. We used microsatellite markers and a 480 bp fragment of the mitochondrial DNA control region to study four polymorphic populations of the Midas cichlid from three crater lakes and one large lake in Nicaragua in an investigation of incipient sympatric speciation. All populations were strongly genetically differentiated on the basis of geography. We identified strong genetic separation based on colour polymorphism for populations from Lake Nicaragua and one crater lake (Lake Apoyo), but failed to find significant genetic structuring based on trophic differences and ecological niche separation in any of the four populations studied. These data support the idea that sexual selection through assortative mating contributes more strongly or earlier during speciation in sympatry than ecological separation in these cichlids. The long-term persistence of divergent cichlid ecotypes (as measured by the percentage sequence divergence between populations) in Central American crater lakes, despite a lack of fixed genetic differentiation, differs strikingly from the patterns of extremely rapid speciation in the cichlids in Africa, including its crater lakes. It is unclear whether extrinsic environmental factors or intrinsic biological differences, e.g. in the degree of phenotypic plasticity, promote different mechanisms and thereby rates of speciation of cichlid fishes from the Old and New Worlds. PMID:11413624

  18. Incipient speciation in sympatric Nicaraguan crater lake cichlid fishes: sexual selection versus ecological diversification.

    PubMed

    Wilson, A B; Noack-Kunnmann, K; Meyer, A

    2000-11-01

    The growing body of empirical evidence for sympatric speciation has been complemented by recent theoretical treatments that have identified evolutionary conditions conducive to speciation in sympatry. The Neotropical Midas cichlid (Amphilophus citrinellum) fits both of the key characteristics of these models, with strong assortative mating on the basis of a colour polymorphism coupled with trophic and ecological differentiation derived from a polymorphism in their pharyngeal jaws. We used microsatellite markers and a 480 bp fragment of the mitochondrial DNA control region to study four polymorphic populations of the Midas cichlid from three crater lakes and one large lake in Nicaragua in an investigation of incipient sympatric speciation. All populations were strongly genetically differentiated on the basis of geography. We identified strong genetic separation based on colour polymorphism for populations from Lake Nicaragua and one crater lake (Lake Apoyo), but failed to find significant genetic structuring based on trophic differences and ecological niche separation in any of the four populations studied. These data support the idea that sexual selection through assortative mating contributes more strongly or earlier during speciation in sympatry than ecological separation in these cichlids. The long-term persistence of divergent cichlid ecotypes (as measured by the percentage sequence divergence between populations) in Central American crater lakes, despite a lack of fixed genetic differentiation, differs strikingly from the patterns of extremely rapid speciation in the cichlids in Africa, including its crater lakes. It is unclear whether extrinsic environmental factors or intrinsic biological differences, e.g. in the degree of phenotypic plasticity, promote different mechanisms and thereby rates of speciation of cichlid fishes from the Old and New Worlds.

  19. Evidence for a Noachian-Aged Ephemeral Lake in Gusev Crater, Mars

    NASA Technical Reports Server (NTRS)

    Ruff, S. W.; Niles, P. B.; Alfano, F.; Clarke, A. B.

    2014-01-01

    Gusev crater was selected as the landing site for the Spirit rover because of the likelihood that it contained an ancient lake. Although outcrops rich in Mg-Fe carbonate dubbed Comanche were discovered in the Noachian-aged Columbia Hills, they were inferred to result from volcanic hydrothermal activity. Spirit encountered other mineral and chemical indicators of aqueous activity, but none was recognized as definitive evidence for a former lake in part because none was associated with obvious lacustrine sedimentary deposits. However, water discharge into Martian crater basins like Gusev may have been episodic, producing only small amounts of sediment and shallow ephemeral lakes. Evaporative precipitation from such water bodies has been suggested as a way of producing the Mg- and Fe-rich carbonates found in ALH84001 and carbonates and salts in some nakhlites a hypothesis we examine for the Comanche carbonate.

  20. Comparison of MTI Water Temperatures with Ground Truth Measurements at Crater Lake, OR

    SciTech Connect

    Kurzeja, R.J.

    2002-12-09

    Water surface temperatures calculated with the Los Alamos National Laboratory Robust algorithm were compared with ground truth water temperature measurements near the Oregon State University buoy in Crater Lake, OR. Bulk water measurements at the OSU buoy were corrected for the skin temperature depression and temperature gradient in the top 10 cm of the water to find the water surface temperature for 18 MTI images for June 2000 to Feb 2002. The MTI robust temperatures were found to be biased by 0.1C, with an RMS error of 1.9C compared with the ground truth water surface temperatures. When corrected for the errors in the buoy temperatures the RMS was reduced to 1.3C. This RMS difference is greater than the 1C found at the Pacific Island of Nauru because of the greater variability in the lake temperature and the atmosphere at Crater Lake and the much smaller target area used in the comparison.

  1. Measurements of spectral optical properties and their relation to biogeochemical variables and processes in Crater Lake, Crater Lake National Park, OR

    USGS Publications Warehouse

    Boss, E.S.; Collier, R.; Larson, G.; Fennel, K.; Pegau, W.S.

    2007-01-01

    Spectral inherent optical properties (IOPs) have been measured at Crater Lake, OR, an extremely clear sub-alpine lake. Indeed Pure water IOPs are major contributors to the total IOPs, and thus to the color of the lake. Variations in the spatial distribution of IOPs were observed in June and September 2001, and reflect biogeochemical processes in the lake. Absorption by colored dissolved organic material increases with depth and between June and September in the upper 300 m. This pattern is consistent with a net release of dissolved organic materials from primary and secondary production through the summer and its photo-oxidation near the surface. Waters fed by a tributary near the lake's rim exhibited low levels of absorption by dissolved organic materials. Scattering is mostly dominated by organic particulate material, though inorganic material is found to enter the lake from the rim following a rain storm. Several similarities to oceanic oligotrophic regions are observed: (a) The Beam attenuation correlates well with particulate organic material (POM) and the relationship is similar to that observed in the open ocean. (b) The specific absorption of colored dissolved organic material has a value similar to that of open ocean humic material. (c) The distribution of chlorophyll with depth does not follow the distribution of particulate organic material due to photo-acclimation resulting in a subsurface pigment maximum located about 50 m below the POM maximum. ?? 2007 Springer Science+Business Media B.V.

  2. Nitrincola nitratireducens sp. nov. isolated from a haloalkaline crater lake.

    PubMed

    Singh, Aditya; Vaidya, Bhumika; Tanuku, Naga Radha Srinivas; Pinnaka, Anil Kumar

    2015-12-01

    The novel, cream coloured, Gram-negative-staining, rod-shaped, motile bacteria, designated strains AK23(T) and AK28, were isolated from sediment samples collected from Lonar Lake, Buldhana district, India. The predominant fatty acids were C18:1ω7c, C16:0, C10:0 3OH and C16:1ω7c and/or iso-C15:0 2OH (summed feature 3). Polar lipid content of strains AK23(T) and AK28 were found to be phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphotidylserine (PS), one unidentified phospholipid (PL) and two unidentified lipids (L1 and L2). The 16S rRNA gene sequence analysis indicated strains AK23(T) and AK28 as the members of the genus Nitrincola and closely related to the type strain Nitrincola lacisaponensis with pair-wise sequence similarity of 97.67% and 97.62% respectively. DNA-DNA hybridization between strain AK23(T) and AK28 showed a relatedness of 91%. Genome of strains AK23(T) and N. lacisaponensis DSM 16316(T) were sequenced. A comparative genomics approach was used to study strains AK23(T), N. lacisaponensis DSM 16316(T) and five other phylogenetic neighbours. The genome size of N. lacisaponensis DSM 16316(T) was found to be 614,784bp smaller than that of the strain AK23(T). This variation could be due to multiple reasons, gene uptake, evolution, mutation, genome reduction phenomenon and draft nature of sequencing. Based on data from the current polyphasic study, strains AK23(T) and AK28 are proposed as novel species of the genus Nitrincola, for which the name Nitrincola nitratireducens sp. nov. is proposed. The type strain of N. nitratireducens is AK23(T) (=JCM 18788(T)=MTCC 11628(T)). PMID:26481633

  3. Nitrincola nitratireducens sp. nov. isolated from a haloalkaline crater lake.

    PubMed

    Singh, Aditya; Vaidya, Bhumika; Tanuku, Naga Radha Srinivas; Pinnaka, Anil Kumar

    2015-12-01

    The novel, cream coloured, Gram-negative-staining, rod-shaped, motile bacteria, designated strains AK23(T) and AK28, were isolated from sediment samples collected from Lonar Lake, Buldhana district, India. The predominant fatty acids were C18:1ω7c, C16:0, C10:0 3OH and C16:1ω7c and/or iso-C15:0 2OH (summed feature 3). Polar lipid content of strains AK23(T) and AK28 were found to be phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphotidylserine (PS), one unidentified phospholipid (PL) and two unidentified lipids (L1 and L2). The 16S rRNA gene sequence analysis indicated strains AK23(T) and AK28 as the members of the genus Nitrincola and closely related to the type strain Nitrincola lacisaponensis with pair-wise sequence similarity of 97.67% and 97.62% respectively. DNA-DNA hybridization between strain AK23(T) and AK28 showed a relatedness of 91%. Genome of strains AK23(T) and N. lacisaponensis DSM 16316(T) were sequenced. A comparative genomics approach was used to study strains AK23(T), N. lacisaponensis DSM 16316(T) and five other phylogenetic neighbours. The genome size of N. lacisaponensis DSM 16316(T) was found to be 614,784bp smaller than that of the strain AK23(T). This variation could be due to multiple reasons, gene uptake, evolution, mutation, genome reduction phenomenon and draft nature of sequencing. Based on data from the current polyphasic study, strains AK23(T) and AK28 are proposed as novel species of the genus Nitrincola, for which the name Nitrincola nitratireducens sp. nov. is proposed. The type strain of N. nitratireducens is AK23(T) (=JCM 18788(T)=MTCC 11628(T)).

  4. A new node on the SE Asian paleoclimate map: the alkaline crater lakes of central Myanmar

    NASA Astrophysics Data System (ADS)

    Smittenberg, Rienk H.; Chabangborn, Akkaneewut; Thu Aung, Lin; Fritz, Sherilyn; Wohlfarth, Barbara

    2014-05-01

    SE Asia is climatically a key region where the Asian monsoon system connects with the Indo-Pacific warm pool and from where much (latent) heat gets transported to higher latitudes. We recently obtained sediment cores from four crater lakes located in Central Myanmar, with the aim to further colour the still largely white space on the SE Asian paleoclimate map. The chain of volcanic craters extending northeast to southwest in the vicinity of the lower Chindwin River in central Myanmar have been known for a long time. These craters are aligned west of the Sagaing Fault, which is a continental transform fault between the Indian and Sunda continental plates. Four of the craters still contain lakes, while several of the smaller craters are drained and used for agriculture. The region has a tropical Savannah climate, with warm temperatures throughout the year. Precipitation is almost absent during the dry season but increases to an average monthly precipitation of 100-134 mm per month during the monsoon season (May through October). Three of the four lakes, named Twin Ywa (30 m depth), Twin Taung (60 m), and Twin Pyauk (8m), are highly alkaline (pH 10-11), support extensive cyanobacterial blooms and are anoxic below a few meters water depth. Their sediments are composed of highly organic and laminated algae gyttjas. The shallower (2m), oxic and more neutral (pH 7.5) Lake Leshe contains organic-lean clays but with clear variations in colour and bulk density that likely mark changes in humidity though time. The lake levels of the relatively small crater lakes are solely regulated by precipitation and evaporation, and their limnology and water isotope compositions are therefore sensitive to changes in monsoon intensity. We will present limnological data including water isotopic compositions, and initial bulk sedimentary data as well as preliminary age determinations. These will form the basis for more extensive multi-proxy analyses that should result in an improved insight

  5. Crater lake habitat predicts morphological diversity in adaptive radiations of cichlid fishes.

    PubMed

    Recknagel, Hans; Elmer, Kathryn R; Meyer, Axel

    2014-07-01

    Adaptive radiations provide an excellent opportunity for studying the correlates and causes for the origin of biodiversity. In these radiations, species diversity may be influenced by either the ecological and physical environment, intrinsic lineage effects, or both. Disentangling the relative contributions of these factors in generating biodiversity remains a major challenge in understanding why a lineage does or does not radiate. Here, we examined morphological variation in body shape for replicate flocks of Nicaraguan Midas cichlid fishes and tested its association with biological and physical characteristics of their crater lakes. We found that variability of body elongation, an adaptive trait in freshwater fishes, is mainly predicted by average lake depth (N = 6, P < 0.001, R(2) = 0.96). Other factors considered, including lake age, surface area, littoral zone area, number of co-occurring fish species, and genetic diversity of the Midas flock, did not significantly predict morphological variability. We also showed that lakes with a larger littoral zone have on average higher bodied Midas cichlids, indicating that Midas cichlid flocks are locally adapted to their crater lake habitats. In conclusion, we found that a lake's habitat predicts the magnitude and the diversity of body elongation in repeated cichlid adaptive radiations.

  6. Crater lake cichlids individually specialize along the benthic-limnetic axis.

    PubMed

    Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel

    2014-04-01

    A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic-limnetic axis in a young adaptive radiation of crater lake cichlid fishes.

  7. Crater lake cichlids individually specialize along the benthic–limnetic axis

    PubMed Central

    Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel

    2014-01-01

    A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic–limnetic axis in a young adaptive radiation of crater lake cichlid fishes. PMID:24772288

  8. Long-term limnological research and monitoring at Crater Lake, Oregon

    USGS Publications Warehouse

    Larson, G.L.; Collier, R.; Buktenica, M.

    2007-01-01

    Crater Lake is located in the caldera of Mount Mazama in Crater Lake National Park, Oregon. The lake has a surface area of about 53 km2at an elevation of 1882 m and a maximum depth of 594 m. Limited studies of this ultraoligotrophic lake conducted between 1896 and 1981, lead to a 10-year limnological study to evaluate any potential degradation of water quality. No long-term variations in water quality were observed that could be attributed to anthropogenic activity. Building on the success of this study, a permanent limnological program has been established with a long-term monitoring program to insure a reliable data base for use in the future. Of equal importance, this program serves as a research platform to develop and communicate to the public a better understanding of the coupled biological, physical, and geochemical processes in the lake and its surrounding environment. This special volume represents our current state of knowledge of the status of this pristine ecosystem including its special optical properties, algal nutrient limitations, pelagic bacteria, and models of the inter-relationships of thermal properties, nutrients, phytoplankton, deep-water mixing, and water budgets. ?? 2007 Springer Science+Business Media B.V.

  9. Crater Lake Apoyo revisited--population genetics of an emerging species flock.

    PubMed

    Geiger, Matthias F; McCrary, Jeffrey K; Schliewen, Ulrich K

    2013-01-01

    The polytypic Nicaraguan Midas cichlids (Amphilophus cf. citrinellus) have been established as a model system for studying the mechanisms of speciation and patterns of diversification in allopatry and sympatry. The species assemblage in Crater Lake Apoyo has been accepted as a textbook example for sympatric speciation. Here, we present a first comprehensive data set of population genetic (mtDNA & AFLPs) proxies of species level differentiation for a representative set of individuals of all six endemic Amphilophus species occurring in Crater Lake Apoyo. AFLP genetic differentiation was partitioned into a neutral and non-neutral component based on outlier-loci detection approaches, and patterns of species divergence were explored with Bayesian clustering methods. Substantial levels of admixture between species were detected, indicating different levels of reproductive isolation between the six species. Analysis of neutral genetic variation revealed several A. zaliosus as being introgressed by an unknown contributor, hereby rendering the sympatrically evolving L. Apoyo flock polyphyletic. This is contrasted by the mtDNA analysis delivering a clear monophyly signal with Crater Lake Apoyo private haplotypes characterising all six described species, but also demonstrating different demographic histories as inferred from pairwise mismatch distributions.

  10. Rapid evolution and selection inferred from the transcriptomes of sympatric crater lake cichlid fishes.

    PubMed

    Elmer, K R; Fan, S; Gunter, H M; Jones, J C; Boekhoff, S; Kuraku, S; Meyer, A

    2010-03-01

    Crater lakes provide a natural laboratory to study speciation of cichlid fishes by ecological divergence. Up to now, there has been a dearth of transcriptomic and genomic information that would aid in understanding the molecular basis of the phenotypic differentiation between young species. We used next-generation sequencing (Roche 454 massively parallel pyrosequencing) to characterize the diversity of expressed sequence tags between ecologically divergent, endemic and sympatric species of cichlid fishes from crater lake Apoyo, Nicaragua: benthic Amphilophus astorquii and limnetic Amphilophus zaliosus. We obtained 24 174 A. astorquii and 21 382 A. zaliosus high-quality expressed sequence tag contigs, of which 13 106 pairs are orthologous between species. Based on the ratio of nonsynonymous to synonymous substitutions, we identified six sequences exhibiting signals of strong diversifying selection (K(a)/K(s) > 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.

  11. Crater Lake Apoyo Revisited - Population Genetics of an Emerging Species Flock

    PubMed Central

    Geiger, Matthias F.; McCrary, Jeffrey K.; Schliewen, Ulrich K.

    2013-01-01

    The polytypic Nicaraguan Midas cichlids (Amphilophus cf. citrinellus) have been established as a model system for studying the mechanisms of speciation and patterns of diversification in allopatry and sympatry. The species assemblage in Crater Lake Apoyo has been accepted as a textbook example for sympatric speciation. Here, we present a first comprehensive data set of population genetic (mtDNA & AFLPs) proxies of species level differentiation for a representative set of individuals of all six endemic Amphilophus species occurring in Crater Lake Apoyo. AFLP genetic differentiation was partitioned into a neutral and non-neutral component based on outlier-loci detection approaches, and patterns of species divergence were explored with Bayesian clustering methods. Substantial levels of admixture between species were detected, indicating different levels of reproductive isolation between the six species. Analysis of neutral genetic variation revealed several A. zaliosus as being introgressed by an unknown contributor, hereby rendering the sympatrically evolving L. Apoyo flock polyphyletic. This is contrasted by the mtDNA analysis delivering a clear monophyly signal with Crater Lake Apoyo private haplotypes characterising all six described species, but also demonstrating different demographic histories as inferred from pairwise mismatch distributions. PMID:24086393

  12. Bacterial Diversity in the Soda Saline Crater Lake from Isabel Island, Mexico.

    PubMed

    Aguirre-Garrido, José Félix; Ramírez-Saad, Hugo César; Toro, Nicolás; Martínez-Abarca, Francisco

    2016-01-01

    Isabel Lake is a moderate saline soda crater lake located in Isabel Island in the eastern tropical Pacific coast of Mexico. Lake is mainly formed by rainfall and is strongly affected by evaporation and high input of nutrients derived from excretions of a large bird community inhabiting the island. So far, only the island macrobiota has been studied. The knowledge of the prokaryotic biota inhabiting the upper layers of this meromictic lake can give clues for the maintenance of this ecosystem. We assessed the diversity and composition of prokaryotic community in sediments and water of the lake by DGGE profiling, 16S rRNA gene amplicon pyrosequencing, and cultivation techniques. The bacterial community is largely dominated by halophilic and halotolerant microorganisms. Alpha diversity estimations reveal higher value in sediments than in water (P > 0.005). The lake water is dominated by γ-Proteobacteria belonging to four main families where Halomonadaceae presents the highest abundance. Aerobic, phototrophic, and halotolerant prokaryotes such as Cyanobacteria GPIIa, Halomonas, Alcanivorax, Idiomarina, and Cyclobacterium genera are commonly found. However, in sediment samples, Formosa, Muricauda, and Salegentibacter genera corresponding to Flavobacteriaceae family accounted for 15-20 % of the diversity. Heterotrophs like those involved in sulfur cycle, Desulfotignum, Desulfuromonas, Desulfofustis, and Desulfopila, appear to play an important role in sediments. Finally, a collection of aerobic halophilic bacterial isolates was created from these samples; members of the genus Halomonas were predominantly isolated from lake water. This study contributes to state the bacterial diversity present in this particular soda saline crater lake.

  13. Bacterial Diversity in the Soda Saline Crater Lake from Isabel Island, Mexico.

    PubMed

    Aguirre-Garrido, José Félix; Ramírez-Saad, Hugo César; Toro, Nicolás; Martínez-Abarca, Francisco

    2016-01-01

    Isabel Lake is a moderate saline soda crater lake located in Isabel Island in the eastern tropical Pacific coast of Mexico. Lake is mainly formed by rainfall and is strongly affected by evaporation and high input of nutrients derived from excretions of a large bird community inhabiting the island. So far, only the island macrobiota has been studied. The knowledge of the prokaryotic biota inhabiting the upper layers of this meromictic lake can give clues for the maintenance of this ecosystem. We assessed the diversity and composition of prokaryotic community in sediments and water of the lake by DGGE profiling, 16S rRNA gene amplicon pyrosequencing, and cultivation techniques. The bacterial community is largely dominated by halophilic and halotolerant microorganisms. Alpha diversity estimations reveal higher value in sediments than in water (P > 0.005). The lake water is dominated by γ-Proteobacteria belonging to four main families where Halomonadaceae presents the highest abundance. Aerobic, phototrophic, and halotolerant prokaryotes such as Cyanobacteria GPIIa, Halomonas, Alcanivorax, Idiomarina, and Cyclobacterium genera are commonly found. However, in sediment samples, Formosa, Muricauda, and Salegentibacter genera corresponding to Flavobacteriaceae family accounted for 15-20 % of the diversity. Heterotrophs like those involved in sulfur cycle, Desulfotignum, Desulfuromonas, Desulfofustis, and Desulfopila, appear to play an important role in sediments. Finally, a collection of aerobic halophilic bacterial isolates was created from these samples; members of the genus Halomonas were predominantly isolated from lake water. This study contributes to state the bacterial diversity present in this particular soda saline crater lake. PMID:26391805

  14. Exploration of Microbial Diversity and Community Structure of Lonar Lake: The Only Hypersaline Meteorite Crater Lake within Basalt Rock.

    PubMed

    Paul, Dhiraj; Kumbhare, Shreyas V; Mhatre, Snehit S; Chowdhury, Somak P; Shetty, Sudarshan A; Marathe, Nachiket P; Bhute, Shrikant; Shouche, Yogesh S

    2015-01-01

    Lonar Lake is a hypersaline and hyperalkaline soda lake and the only meteorite impact crater in the world situated in basalt rocks. Although culture-dependent studies have been reported, a comprehensive understanding of microbial community composition and structure in Lonar Lake remains elusive. In the present study, microbial community structure associated with Lonar Lake sediment and water samples was investigated using high-throughput sequencing. Microbial diversity analysis revealed the existence of diverse, yet largely consistent communities. Proteobacteria (30%), Actinobacteria (24%), Firmicutes (11%), and Cyanobacteria (5%) predominated in the sequencing survey, whereas Bacteroidetes (1.12%), BD1-5 (0.5%), Nitrospirae (0.41%), and Verrucomicrobia (0.28%) were detected in relatively minor abundances in the Lonar Lake ecosystem. Within the Proteobacteria phylum, the Gammaproteobacteria represented the most abundantly detected class (21-47%) within sediment samples, but only a minor population in the water samples. Proteobacteria and Firmicutes were found at significantly higher abundance (p ≥ 0.05) in sediment samples, whereas members of Actinobacteria, Candidate division TM7 and Cyanobacteria (p ≥ 0.05) were significantly abundant in water samples. Compared to the microbial communities of other hypersaline soda lakes, those of Lonar Lake formed a distinct cluster, suggesting a different microbial community composition and structure. Here we report for the first time, the difference in composition of indigenous microbial communities between the sediment and water samples of Lonar Lake. An improved census of microbial community structure in this Lake ecosystem provides a foundation for exploring microbial biogeochemical cycling and microbial function in hypersaline lake environments.

  15. Exploration of Microbial Diversity and Community Structure of Lonar Lake: The Only Hypersaline Meteorite Crater Lake within Basalt Rock.

    PubMed

    Paul, Dhiraj; Kumbhare, Shreyas V; Mhatre, Snehit S; Chowdhury, Somak P; Shetty, Sudarshan A; Marathe, Nachiket P; Bhute, Shrikant; Shouche, Yogesh S

    2015-01-01

    Lonar Lake is a hypersaline and hyperalkaline soda lake and the only meteorite impact crater in the world situated in basalt rocks. Although culture-dependent studies have been reported, a comprehensive understanding of microbial community composition and structure in Lonar Lake remains elusive. In the present study, microbial community structure associated with Lonar Lake sediment and water samples was investigated using high-throughput sequencing. Microbial diversity analysis revealed the existence of diverse, yet largely consistent communities. Proteobacteria (30%), Actinobacteria (24%), Firmicutes (11%), and Cyanobacteria (5%) predominated in the sequencing survey, whereas Bacteroidetes (1.12%), BD1-5 (0.5%), Nitrospirae (0.41%), and Verrucomicrobia (0.28%) were detected in relatively minor abundances in the Lonar Lake ecosystem. Within the Proteobacteria phylum, the Gammaproteobacteria represented the most abundantly detected class (21-47%) within sediment samples, but only a minor population in the water samples. Proteobacteria and Firmicutes were found at significantly higher abundance (p ≥ 0.05) in sediment samples, whereas members of Actinobacteria, Candidate division TM7 and Cyanobacteria (p ≥ 0.05) were significantly abundant in water samples. Compared to the microbial communities of other hypersaline soda lakes, those of Lonar Lake formed a distinct cluster, suggesting a different microbial community composition and structure. Here we report for the first time, the difference in composition of indigenous microbial communities between the sediment and water samples of Lonar Lake. An improved census of microbial community structure in this Lake ecosystem provides a foundation for exploring microbial biogeochemical cycling and microbial function in hypersaline lake environments. PMID:26834712

  16. Exploration of Microbial Diversity and Community Structure of Lonar Lake: The Only Hypersaline Meteorite Crater Lake within Basalt Rock

    PubMed Central

    Paul, Dhiraj; Kumbhare, Shreyas V.; Mhatre, Snehit S.; Chowdhury, Somak P.; Shetty, Sudarshan A.; Marathe, Nachiket P.; Bhute, Shrikant; Shouche, Yogesh S.

    2016-01-01

    Lonar Lake is a hypersaline and hyperalkaline soda lake and the only meteorite impact crater in the world situated in basalt rocks. Although culture-dependent studies have been reported, a comprehensive understanding of microbial community composition and structure in Lonar Lake remains elusive. In the present study, microbial community structure associated with Lonar Lake sediment and water samples was investigated using high-throughput sequencing. Microbial diversity analysis revealed the existence of diverse, yet largely consistent communities. Proteobacteria (30%), Actinobacteria (24%), Firmicutes (11%), and Cyanobacteria (5%) predominated in the sequencing survey, whereas Bacteroidetes (1.12%), BD1-5 (0.5%), Nitrospirae (0.41%), and Verrucomicrobia (0.28%) were detected in relatively minor abundances in the Lonar Lake ecosystem. Within the Proteobacteria phylum, the Gammaproteobacteria represented the most abundantly detected class (21–47%) within sediment samples, but only a minor population in the water samples. Proteobacteria and Firmicutes were found at significantly higher abundance (p ≥ 0.05) in sediment samples, whereas members of Actinobacteria, Candidate division TM7 and Cyanobacteria (p ≥ 0.05) were significantly abundant in water samples. Compared to the microbial communities of other hypersaline soda lakes, those of Lonar Lake formed a distinct cluster, suggesting a different microbial community composition and structure. Here we report for the first time, the difference in composition of indigenous microbial communities between the sediment and water samples of Lonar Lake. An improved census of microbial community structure in this Lake ecosystem provides a foundation for exploring microbial biogeochemical cycling and microbial function in hypersaline lake environments. PMID:26834712

  17. Small changes in climate can profoundly alter the dynamics and ecosystem services of tropical crater lakes.

    PubMed

    Saulnier-Talbot, Émilie; Gregory-Eaves, Irene; Simpson, Kyle G; Efitre, Jackson; Nowlan, Tobias E; Taranu, Zofia E; Chapman, Lauren J

    2014-01-01

    African tropical lakes provide vital ecosystem services including food and water to some of the fastest growing human populations, yet they are among the most understudied ecosystems in the world. The consequences of climate change and other stressors on the tropical lakes of Africa have been informed by long-term analyses, but these studies have largely focused on the massive Great Rift Valley lakes. Our objective was to evaluate how recent climate change has altered the functioning and services of smaller tropical lakes, which are far more abundant on the landscape. Based on a paired analysis of 20 years of high-resolution water column data and a paleolimnological record from a small crater lake in western Uganda, we present evidence that even a modest warming of the air (∼0.9°C increase over 20 years) and changes in the timing and intensity of rainfall can have significant consequences on the dynamics of this common tropical lake type. For example, we observed a significant nonlinear increase (R(2) adj  = 0.23, e.d.f. = 7, p<0.0001) in thermal stability over the past 20 years. This resulted in the expansion of anoxic waters and consequent deterioration of fish habitat and appears to have abated primary production; processes that may impair ecosystem services for a vulnerable human population. This study on a system representative of small tropical crater lakes highlights the far-reaching effects of global climatic change on tropical waters. Increased research efforts into tropical aquatic ecosystem health and the development of sound management practices are necessary in order to strengthen adaptive capabilities in tropical regions.

  18. Small Changes in Climate Can Profoundly Alter the Dynamics and Ecosystem Services of Tropical Crater Lakes

    PubMed Central

    Saulnier-Talbot, Émilie; Gregory-Eaves, Irene; Simpson, Kyle G.; Efitre, Jackson; Nowlan, Tobias E.; Taranu, Zofia E.; Chapman, Lauren J.

    2014-01-01

    African tropical lakes provide vital ecosystem services including food and water to some of the fastest growing human populations, yet they are among the most understudied ecosystems in the world. The consequences of climate change and other stressors on the tropical lakes of Africa have been informed by long-term analyses, but these studies have largely focused on the massive Great Rift Valley lakes. Our objective was to evaluate how recent climate change has altered the functioning and services of smaller tropical lakes, which are far more abundant on the landscape. Based on a paired analysis of 20 years of high-resolution water column data and a paleolimnological record from a small crater lake in western Uganda, we present evidence that even a modest warming of the air (∼0.9°C increase over 20 years) and changes in the timing and intensity of rainfall can have significant consequences on the dynamics of this common tropical lake type. For example, we observed a significant nonlinear increase (R2adj = 0.23, e.d.f. = 7, p<0.0001) in thermal stability over the past 20 years. This resulted in the expansion of anoxic waters and consequent deterioration of fish habitat and appears to have abated primary production; processes that may impair ecosystem services for a vulnerable human population. This study on a system representative of small tropical crater lakes highlights the far-reaching effects of global climatic change on tropical waters. Increased research efforts into tropical aquatic ecosystem health and the development of sound management practices are necessary in order to strengthen adaptive capabilities in tropical regions. PMID:24497954

  19. Small changes in climate can profoundly alter the dynamics and ecosystem services of tropical crater lakes.

    PubMed

    Saulnier-Talbot, Émilie; Gregory-Eaves, Irene; Simpson, Kyle G; Efitre, Jackson; Nowlan, Tobias E; Taranu, Zofia E; Chapman, Lauren J

    2014-01-01

    African tropical lakes provide vital ecosystem services including food and water to some of the fastest growing human populations, yet they are among the most understudied ecosystems in the world. The consequences of climate change and other stressors on the tropical lakes of Africa have been informed by long-term analyses, but these studies have largely focused on the massive Great Rift Valley lakes. Our objective was to evaluate how recent climate change has altered the functioning and services of smaller tropical lakes, which are far more abundant on the landscape. Based on a paired analysis of 20 years of high-resolution water column data and a paleolimnological record from a small crater lake in western Uganda, we present evidence that even a modest warming of the air (∼0.9°C increase over 20 years) and changes in the timing and intensity of rainfall can have significant consequences on the dynamics of this common tropical lake type. For example, we observed a significant nonlinear increase (R(2) adj  = 0.23, e.d.f. = 7, p<0.0001) in thermal stability over the past 20 years. This resulted in the expansion of anoxic waters and consequent deterioration of fish habitat and appears to have abated primary production; processes that may impair ecosystem services for a vulnerable human population. This study on a system representative of small tropical crater lakes highlights the far-reaching effects of global climatic change on tropical waters. Increased research efforts into tropical aquatic ecosystem health and the development of sound management practices are necessary in order to strengthen adaptive capabilities in tropical regions. PMID:24497954

  20. The enigmatic Zerelia twin-lakes (Thessaly, Central Greece): two potential meteorite impact Craters

    NASA Astrophysics Data System (ADS)

    Dietrich, V. J.; Lagios, E.; Reusser, E.; Sakkas, V.; Gartzos, E.; Kyriakopoulos, K.

    2013-09-01

    Two circular permanent lakes of 150 and 250 m diameter and 6-8 m depth to an unconsolidated muddy bottom occur 250 m apart from each other in the agricultural fields SW of the town of Almiros (Thessaly, central Greece). The age of the lakes is assumed to be Late Pliocene to Early Holocene with a minimum age of approx. 7000 yr BP. The abundant polymict, quartz-rich carbonate breccia and clasts with a clay rich matrix in the shallow embankments of the lakes show weak stratification but no volcanic structures. The carbonate clasts and particles often display spheroidal shapes and consist of calcite aggregates with feathery, arborescent, variolitic to micro-sparitic textures and spheroidal fabrics, recrystallized and deformed glass-shaped fragments, calcite globules in quartz; thus indications of possible carbonate melting, quenching and devitrification. The carbonatic matrix includes small xenomorphic phases, such as chromspinel, zircon with blurred granular and skeletal textures, skeletal rutile and ilmenite, which are interpreted as relicts of partial melting and quenching under high temperatures of 1240-1800 °C. Only a few quartz fragments exhibit indistinct planar fractures. In several cases they include exotic Al-Si- and sulfur bearing Fe-phases, < 1-10 μm as globules. The modeled "Residual Gravity" profiles through the lakes indicate negative gravity anomalies of bowl-type structures down to 150 m for the eastern lake and down to 250 m for the larger western lake. Several hypotheses can be drawn upon to explain the origin of these enigmatic twin-lakes: (a) Maar-type volcanic craters; (b) hydrothermal or CO2/hydrocarbon gas explosion craters; (c) and (d) doline holes due to karstification; or (e) small meteorite impact craters, the latter being a plausible explanation due to geologic, petrologic, and geophysical evidence. The morphology and dimensions of the lakes as well as the density contrast tomography of the bedrock favor a meteorite impact hypothesis of a

  1. Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 years

    NASA Astrophysics Data System (ADS)

    Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

    2014-08-01

    Equatorial East Africa has a complex regional patchwork of climate regimes, sensitive to climate fluctuations over a variety of temporal and spatial scales during the late Holocene. Understanding how these changes are recorded in and interpreted from biological and geochemical proxies in lake sedimentary records remains a key challenge to answering fundamental questions regarding the nature, spatial extent and synchroneity of climatic changes seen in East African palaeo-records. Using a paired lake approach, where neighbouring lakes share the same geology, climate and landscape, it might be expected that the systems will respond similarly to external climate forcing. Sediment cores from two crater lakes in western Uganda spanning the last ~1000 years were examined to assess diatom community responses to late Holocene climate and environmental changes, and to test responses to multiple drivers using redundancy analysis (RDA). These archives provide annual to sub-decadal records of environmental change. Lakes Nyamogusingiri and Kyasanduka appear to operate as independent systems in their recording of a similar hydrological response signal via distinct diatom records. However, whilst their fossil diatom records demonstrate an individualistic, indirect response to external (e.g. climatic) drivers, the inferred lake levels show similar overall trends and reflect the broader patterns observed in Uganda and across East Africa. The lakes appear to be sensitive to large-scale climatic perturbations, with evidence of a dry Medieval Climate Anomaly (MCA; ca. AD 1000-1200). The diatom record from Lake Nyamogusingiri suggests a drying climate during the main phase of the Little Ice Age (LIA) (ca. AD 1600-1800), whereas the diatom response from the shallower Lake Kyasanduka is more complex (with groundwater likely playing a key role), and may be driven more by changes in silica and other nutrients, rather than by lake level. The sensitivity of these two Ugandan lakes to regional

  2. Introduced predator elicits deficient brood defence behaviour in a crater lake fish.

    PubMed

    Lehtonen, Topi K; McCrary, Jeffrey K; Meyer, Axel

    2012-01-01

    Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloá, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire.

  3. Introduced Predator Elicits Deficient Brood Defence Behaviour in a Crater Lake Fish

    PubMed Central

    Lehtonen, Topi K.; McCrary, Jeffrey K.; Meyer, Axel

    2012-01-01

    Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloá, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire. PMID:22253881

  4. Cruise report R/V Surf Surveyor cruise S1-00-CL, mapping the bathymetry of Crater Lake, Oregon

    USGS Publications Warehouse

    Gardner, James V.; Mayer, Larry A.; Buktenica, Mark W.

    2000-01-01

    During the Spring of 1999, the US Geological Survey (USGS) Pacific Seafloor Mapping Project (PSMP) was contacted by the US National Park Service Crater Lake National Park (CLNP) to inquire about the plausibility of producing a high-resolution multibeam bathymetric map of Crater Lake. The purpose was to generate a much higher-resolution and more geographically accurate bathymetric map than was produced in 1959, the last time the lake had been surveyed. Scientific interest in various aspects of Crater Lake (aquatic biology, geochemistry, volcanic processes, etc.) has increased during the past decade but the basemap of bathymetry was woefully inadequate. Funds were gathered during the early part of 2000 and the mapping began in late July, 2000. Crater Lake (see fig. 1 in report) is located in south central Oregon (see fig. 2 in report) within the Cascades Range, a chain of volcanoes that stretches from northern California to southern British Columbia. Crater Lake is the collapsed caldera of Mt. Mazama from a climatic eruption about 7700-yr ago (Nelson et al., 1988; Bacon and Lanphere, 1990; Bacon et al., 1997). The floor of Crater Lake has only been mapped three times since the lake was first stumbled upon by gold prospectors in the 1853. The first survey was carried by out by William G. Steel during a joint USGS-US Army expedition under the direction of Maj. Clarence E. Dutton in 1886 (Dutton, 1889). Steel�s mapping survey collected 186 soundings using a Millers lead-line sounding machine (see fig.3 in report). The resulting map (see fig.4 in report) shows only soundings and no attempts were made to generate contours. The second survey, conducted in 1959 by the US Coast and Geodetic Survey, mapped the bathymetry of Crater Lake with an acoustic echo sounder using radar navigation and collected 4000 soundings. The data were contoured by Williams (1961) and Byrne (1962) and the result is a fairly detailed map of the large-scale features of Crater Lake (see fig. 5

  5. 2000 Multibeam Sonar Survey of Crater Lake, Oregon - Data, GIS, Images, and Movies

    USGS Publications Warehouse

    Gardner, James V.; Dartnell, Peter

    2001-01-01

    In the summer of 2000, the U.S. Geological Survey, Pacific Seafloor Mapping Project in cooperation with the National Park Service, and the Center for Coastal and Ocean Mapping, University of New Hampshire used a state-of-the-art multibeam sonar system to collect high-resolution bathymetry and calibrated, co-registered acoustic backscatter to support both biological and geological research in the Crater Lake area. This interactive CD-ROM contains the multibeam bathymetry and acoustic backscatter data, along with an ESRI ArcExplorer project (and software), images, and movies.

  6. High spatio-temporal resolution observations of crater lake temperatures at Kawah Ijen volcano, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Lewicki, Jennifer L.; Caudron, Corentin; van Hinsberg, Vincent J.; Hilley, George E.

    2016-08-01

    The crater lake of Kawah Ijen volcano, East Java, Indonesia, has displayed large and rapid changes in temperature at point locations during periods of unrest, but measurement techniques employed to date have not resolved how the lake's thermal regime has evolved over both space and time. We applied a novel approach for mapping and monitoring variations in crater lake apparent surface ("skin") temperatures at high spatial (˜32 cm) and temporal (every 2 min) resolution at Kawah Ijen on 18 September 2014. We used a ground-based FLIR T650sc camera with digital and thermal infrared (TIR) sensors from the crater rim to collect (1) a set of visible imagery around the crater during the daytime and (2) a time series of co-located visible and TIR imagery at one location from pre-dawn to daytime. We processed daytime visible imagery with the Structure-from-Motion photogrammetric method to create a digital elevation model onto which the time series of TIR imagery was orthorectified and georeferenced. Lake apparent skin temperatures typically ranged from ˜21 to 33 °C. At two locations, apparent skin temperatures were ˜4 and 7 °C less than in situ lake temperature measurements at 1.5 and 5-m depth, respectively. These differences, as well as the large spatio-temporal variations observed in skin temperatures, were likely largely associated with atmospheric effects such as the evaporative cooling of the lake surface and infrared absorption by water vapor and SO2. Calculations based on orthorectified TIR imagery thus yielded underestimates of volcanic heat fluxes into the lake, whereas volcanic heat fluxes estimated based on in situ temperature measurements (68 to 111 MW) were likely more representative of Kawah Ijen in a quiescent state. The ground-based imaging technique should provide a valuable tool to continuously monitor crater lake temperatures and contribute insight into the spatio-temporal evolution of these temperatures associated with volcanic activity.

  7. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake.

    PubMed

    Malinsky, Milan; Challis, Richard J; Tyers, Alexandra M; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P; Miska, Eric A; Durbin, Richard; Genner, Martin J; Turner, George F

    2015-12-18

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology. With whole-genome sequences of 146 fish, we identified 98 clearly demarcated genomic "islands" of high differentiation and demonstrated the association of genotypes across these islands with divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight-vision-associated genes), hormone signaling, and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi. PMID:26680190

  8. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake.

    PubMed

    Malinsky, Milan; Challis, Richard J; Tyers, Alexandra M; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P; Miska, Eric A; Durbin, Richard; Genner, Martin J; Turner, George F

    2015-12-18

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology. With whole-genome sequences of 146 fish, we identified 98 clearly demarcated genomic "islands" of high differentiation and demonstrated the association of genotypes across these islands with divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight-vision-associated genes), hormone signaling, and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi.

  9. Parallel evolution of Nicaraguan crater lake cichlid fishes via non-parallel routes.

    PubMed

    Elmer, Kathryn R; Fan, Shaohua; Kusche, Henrik; Spreitzer, Maria Luise; Kautt, Andreas F; Franchini, Paolo; Meyer, Axel

    2014-10-27

    Fundamental to understanding how biodiversity arises and adapts is whether evolution is predictable in the face of stochastic genetic and demographic factors. Here we show rapid parallel evolution across two closely related but geographically isolated radiations of Nicaraguan crater lake cichlid fishes. We find significant morphological, ecological and genetic differentiation between ecomorphs in sympatry, reflected primarily in elongated versus high-bodied shape, differential ecological niche use and genetic differentiation. These eco-morphological divergences are significantly parallel across radiations. Based on 442,644 genome-wide single nucleotide polymorphisms, we identify strong support for the monophyly of, and subsequent sympatric divergence within, each radiation. However, the order of speciation differs across radiations; in one lake the limnetic ecomorph diverged first while in the other a benthic ecomorph. Overall our results demonstrate that complex parallel phenotypes can evolve very rapidly and repeatedly in similar environments, probably due to natural selection, yet this evolution can proceed along different evolutionary genetic routes.

  10. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake*

    PubMed Central

    Tyers, Alexandra M.; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P.; Miska, Eric A.; Durbin, Richard; Genner, Martin J.; Turner, George F.

    2015-01-01

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here, we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700m diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet and trophic morphology. With whole genome sequences of 146 fish, we identify 98 clearly demarcated genomic ‘islands’ of high differentiation and demonstrate association of genotypes across these islands to divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight vision associated genes), hormone signaling and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi. PMID:26680190

  11. Boiling Lake of Dominica, West Indies: High-temperature volcanic crater lake dynamics

    NASA Astrophysics Data System (ADS)

    Fournier, N.; Witham, F.; Moreau-Fournier, M.; Bardou, L.

    2009-02-01

    The Boiling Lake of Dominica has exhibited stable high-temperature behavior for at least 150 a. This stability is punctuated by occasional crises involving rapid filling and draining of the lake and changes in water temperature. The most recent such crisis occurred in December 2004 to April 2005. Using the results of previous theoretical and experimental work on analogue models, we present a combined thermal, hydrological, and fluid mechanical model of the Boiling Lake. This reveals that the lake appears to be suspended above the local water table by a constant supply of rising steam bubbles sourced from the boiling of groundwater near an igneous intrusion. The bubbles condense in the Boiling Lake, maintaining the temperature at ˜90°C. The geometry of the lake-conduit system provides a mechanism for instability, with a denser liquid lake overlying a bubbly fractured permeable conduit. Following a sufficiently large perturbation, the whole lake rapidly drains until the surface is at the local water table level. The persistent gas supply then reinitiates filling. We propose that local seismic activity may have caused shock nucleation of bubbles within the conduit and triggered the instability of the Boiling Lake.

  12. Ice-Covered Lakes in Gale Crater Mars: The Cold and Wet Hypothesis

    NASA Astrophysics Data System (ADS)

    Kling, Alexandre; Haberle, Robert; McKay, Christopher P.; Bristow, Thomas

    2016-10-01

    Recent geological discoveries from the Mars Science Laboratory provide evidence that Gale crater may have intermittently hosted a fluvio-lacustine environment during the Hesperian, with individual lakes lasting for a period of tens to hundreds of thousands of years. (Grotzinger et al., Science, 350 (6257), 2015). Estimates of the CO2 content of the atmosphere at the time the Gale sediments formed are far less than needed by any climate model to warm early Mars (Bristow et al., Geology, submitted), given the low solar energy input available at Mars 3.5 Gya. We have therefore explored the possibility that the lakes in Gale during the Hesperian were perennially covered with ice using the Antarctic Lakes as an analog. Using our best estimate for the annual mean surface temperature at Gale at this time (~230K) we computed the thickness of an ice-covered lake. These thickness range from 10-30 meters depending on the ablation rate and ice transparency and would likely inhibit sediments from entering the lake. Thus, a first conclusion is that the ice must not be too cold. Raising the mean temperature to 245K is challenging, but not quite as hard as reaching 273K. We found that a mean annual temperature of 245K ice thicknesses range from 3-10 meters. These values are comparable to the range of those for the Antarctic lakes (3-6 m), and are not implausible. And they are not so thick that sediments cannot penetrate the ice. For the ice-covered lake hypothesis to work, however, a melt water source is needed. This could come from subaqueous melting of a glacial dam in contact with the lakes (as is the case for Lake Untersee) or from seasonal melt water from nearby glaciers (as is the case for the Dry Valley lakes). More work is needed to better assess these possibilities. However, the main advantage of the ice-covered lake model (and the main reason we pursued it) is that it relaxes the requirement for a long-lived active hydrological cycle involving rainfall and runoff, which

  13. Simulation of deep ventilation in Crater Lake, Oregon, 1951–2099

    USGS Publications Warehouse

    Wood, Tamara M.; Wherry, Susan A.; Piccolroaz, Sebastiano; Girdner, Scott F

    2016-01-01

    The frequency of deep ventilation events in Crater Lake, a caldera lake in the Oregon Cascade Mountains, was simulated in six future climate scenarios, using a 1-dimensional deep ventilation model (1DDV) that was developed to simulate the ventilation of deep water initiated by reverse stratification and subsequent thermobaric instability. The model was calibrated and validated with lake temperature data collected from 1994 to 2011. Wind and air temperature data from three general circulation models and two representative concentration pathways were used to simulate the change in lake temperature and the frequency of deep ventilation events in possible future climates. The lumped model air2water was used to project lake surface temperature, a required boundary condition for the lake model, based on air temperature in the future climates.The 1DDV model was used to simulate daily water temperature profiles through 2099. All future climate scenarios projected increased water temperature throughout the water column and a substantive reduction in the frequency of deep ventilation events. The least extreme scenario projected the frequency of deep ventilation events to decrease from about 1 in 2 years in current conditions to about 1 in 3 years by 2100. The most extreme scenario considered projected the frequency of deep ventilation events to be about 1 in 7.7 years by 2100. All scenarios predicted that the temperature of the entire water column will be greater than 4 °C for increasing lengths of time in the future and that the conditions required for thermobaric instability induced mixing will become rare or non-existent.The disruption of deep ventilation by itself does not provide a complete picture of the potential ecological and water quality consequences of warming climate to Crater Lake. Estimating the effect of warming climate on deep water oxygen depletion and water clarity will require careful modeling studies to combine the physical mixing processes affected by

  14. Simulation of deep ventilation in Crater Lake, Oregon, 1951–2099

    USGS Publications Warehouse

    Wood, Tamara M.; Wherry, Susan A.; Piccolroaz, Sebastiano; Girdner, Scott F

    2016-05-04

    The frequency of deep ventilation events in Crater Lake, a caldera lake in the Oregon Cascade Mountains, was simulated in six future climate scenarios, using a 1-dimensional deep ventilation model (1DDV) that was developed to simulate the ventilation of deep water initiated by reverse stratification and subsequent thermobaric instability. The model was calibrated and validated with lake temperature data collected from 1994 to 2011. Wind and air temperature data from three general circulation models and two representative concentration pathways were used to simulate the change in lake temperature and the frequency of deep ventilation events in possible future climates. The lumped model air2water was used to project lake surface temperature, a required boundary condition for the lake model, based on air temperature in the future climates.The 1DDV model was used to simulate daily water temperature profiles through 2099. All future climate scenarios projected increased water temperature throughout the water column and a substantive reduction in the frequency of deep ventilation events. The least extreme scenario projected the frequency of deep ventilation events to decrease from about 1 in 2 years in current conditions to about 1 in 3 years by 2100. The most extreme scenario considered projected the frequency of deep ventilation events to be about 1 in 7.7 years by 2100. All scenarios predicted that the temperature of the entire water column will be greater than 4 °C for increasing lengths of time in the future and that the conditions required for thermobaric instability induced mixing will become rare or non-existent.The disruption of deep ventilation by itself does not provide a complete picture of the potential ecological and water quality consequences of warming climate to Crater Lake. Estimating the effect of warming climate on deep water oxygen depletion and water clarity will require careful modeling studies to combine the physical mixing processes affected by

  15. Genomic architecture of ecologically divergent body shape in a pair of sympatric crater lake cichlid fishes.

    PubMed

    Franchini, Paolo; Fruciano, Carmelo; Spreitzer, Maria L; Jones, Julia C; Elmer, Kathryn R; Henning, Frederico; Meyer, Axel

    2014-04-01

    Determining the genetic bases of adaptations and their roles in speciation is a prominent issue in evolutionary biology. Cichlid fish species flocks are a prime example of recent rapid radiations, often associated with adaptive phenotypic divergence from a common ancestor within a short period of time. In several radiations of freshwater fishes, divergence in ecomorphological traits - including body shape, colour, lips and jaws - is thought to underlie their ecological differentiation, specialization and, ultimately, speciation. The Midas cichlid species complex (Amphilophus spp.) of Nicaragua provides one of the few known examples of sympatric speciation where species have rapidly evolved different but parallel morphologies in young crater lakes. This study identified significant QTL for body shape using SNPs generated via ddRAD sequencing and geometric morphometric analyses of a cross between two ecologically and morphologically divergent, sympatric cichlid species endemic to crater Lake Apoyo: an elongated limnetic species (Amphilophus zaliosus) and a high-bodied benthic species (Amphilophus astorquii). A total of 453 genome-wide informative SNPs were identified in 240 F2 hybrids. These markers were used to construct a genetic map in which 25 linkage groups were resolved. Seventy-two segregating SNPs were linked to 11 QTL. By annotating the two most highly supported QTL-linked genomic regions, genes that might contribute to divergence in body shape along the benthic-limnetic axis in Midas cichlid sympatric adaptive radiations were identified. These results suggest that few genomic regions of large effect contribute to early stage divergence in Midas cichlids.

  16. Indications of fluid immiscibility in glass from West Clearwater Lake impact crater, Quebec, Canada

    NASA Technical Reports Server (NTRS)

    Dence, M. R.; Von Engelhardt, W.; Plant, A. G.; Walter, L. S.

    1974-01-01

    Glass from the West Clearwater Lake hypervelocity impact crater contains numerous spheroids, 10 to 500 microns across, which appear to have formed at high temperatures as fluids immiscible in the enclosing melt. The spheroids are distinguished from small, normal, largely void gas vesicles, which are also present, by being completely filled in all cases; by having fillings which vary in composition from spheroid to spheroid, even between spheroids in close association; and by indications that the present fillings are representative of the contents present before the matrix melt chilled. Most of the spheroids are classified petrographically into three types. The preservation of spheroids in the West Clearwater Lake glass is attributed mainly to the position of the glass masses within the breccias lining the crater floor. It is considered that the glass in this location did not achieve free flight but, as part of a large mass, cooled relatively slowly through the high temperature regime in which the spheroids were generated, and then, when detached, chilled rapidly to preserve a record of this transient stage in their history.

  17. Multibeam Sonar Mapping and Modeling of a Submerged Bryophyte Mat in Crater Lake, Oregon

    USGS Publications Warehouse

    Dartnell, Peter; Collier, Robert; Buktenica, Mark; Jessup, Steven; Girdner, Scott; Triezenberg, Peter

    2008-01-01

    Traditionally, multibeam data have been used to map sea floor or lake floor morphology as well as the distribution of surficial facies in order to characterize the geologic component of benthic habitats. In addition to using multibeam data for geologic studies, we want to determine if these data can also be used directly to map the distribution of biota. Multibeam bathymetry and acoustic backscatter data collected in Crater Lake, Oregon, in 2000 are used to map the distribution of a deep-water bryophyte mat, which will be extremely useful for understanding the overall ecology of the lake. To map the bryophyte's distribution, depth range, acoustic backscatter intensity, and derived bathymetric index grids are used as inputs into a hierarchical decision-tree classification model. Observations of the bryophyte mat from over 23 line kilometers of lake-floor video collected in the summer of 2006 are used as controls for the model. The resulting map matches well with ground-truth information and shows that the bryophyte mat covers most of the platform surrounding Wizard Island as well as on outcrops around the caldera wall.

  18. Simulation of Deep Water Renewal in Crater Lake, Oregon, USA under Current and Future Climate Conditions

    NASA Astrophysics Data System (ADS)

    Piccolroaz, S.; Wood, T. M.; Wherry, S.; Girdner, S.

    2015-12-01

    We applied a 1-dimensional lake model developed to simulate deep mixing related to thermobaric instabilities in temperate lakes to Crater Lake, a 590-m deep caldera lake in Oregon's Cascade Range known for its stunning deep blue color and extremely clear water, in order to determine the frequency of deep water renewal in future climate conditions. The lake model was calibrated with 6 years of water temperature profiles, and then simulated 10 years of validation data with an RMSE ranging from 0.81°C at 50 m depth to 0.04°C at 350-460 m depth. The simulated time series of heat content in the deep lake accurately captured extreme years characterized by weak and strong deep water renewal. The lake model uses wind speed and lake surface temperature (LST) as boundary conditions. LST projections under six climate scenarios from the CMIP5 intermodel comparison project (2 representative concentration pathways X 3 general circulation models) were evaluated with air2water, a simple lumped model that only requires daily values of downscaled air temperature. air2water was calibrated with data from 1993-2011, resulting in a RMSE between simulated and observed daily LST values of 0.68°C. All future climate scenarios project increased water temperature throughout the water column and a substantive reduction in the frequency of deepwater renewal events. The least extreme scenario (CNRM-CM5, RCP4.5) projects the frequency of deepwater renewal events to decrease from about 1 in 2 years in the present to about 1 in 3 years by 2100. The most extreme scenario (HadGEM2-ES, RCP8.5) projects the frequency of deepwater renewal events to be less than 1 in 7 years by 2100 and lake surface temperatures never cooling to less than 4°C after 2050. In all RCP4.5 simulations the temperature of the entire water column is greater than 4°C for increasing periods of time. In the RCP8.5 simulations, the temperature of the entire water column is greater than 4°C year round by the year 2060 (HadGEM2

  19. Controls on lava lake level at Halema`uma`u Crater, Kilauea Volcano

    NASA Astrophysics Data System (ADS)

    Patrick, M. R.; Orr, T. R.

    2013-12-01

    Lava level is a fundamental measure of lava lake activity, but very little continuous long-term data exist worldwide to explore this aspect of lava lake behavior. The ongoing summit eruption at Kilauea Volcano began in 2008 and is characterized by an active lava lake within the eruptive vent. Lava level has been measured nearly continuously at Kilauea for several years using a combination of webcam images, laser rangefinder, and terrestrial LIDAR. Fluctuations in lava level have been a common aspect of the eruption and occur over several timescales. At the shortest timescale, the lava lake level can change over seconds to hours owing to two observed shallow gas-related processes. First, gas pistoning is common and is driven by episodic gas accumulation and release from the surface of the lava lake, causing the lava level to rise and fall by up to 20 m. Second, rockfalls into the lake trigger abrupt gas release, and lava level may drop as much as 10 m as a result. Over days, cyclic changes in lava level closely track cycles of deflation-inflation (DI) deformation events at the summit, leading to level changes up to 50 m. Rift zone intrusions have caused large (up to 140 m) drops in lava level over several days. On the timescale of weeks to months, the lava level follows the long-term inflation and deflation of the summit region, resulting in level changes up to 140 m. The remarkable correlation between lava level and deflation-inflation cycles, as well as the long-term deformation of the summit region, indicates that the lava lake acts as a reliable 'piezometer' (a measure of liquid pressure in the magma plumbing system); therefore, assessments of summit pressurization (and rift zone eruption potential) can now be carried out with the naked eye. The summit lava lake level is closely mirrored by the lava level within Pu`u `O`o crater, the vent area for the 30-year-long eruption on Kilauea's east rift zone, which is 20 km downrift of the summit. The coupling of these

  20. Pseudorhodobacter sinensis sp. nov. and Pseudorhodobacter aquaticus sp. nov., isolated from crater lakes.

    PubMed

    Li, Ai-Hua; Liu, Hong-Can; Hou, Wei-Guo; Zhou, Yu-Guang

    2016-08-01

    Three Gram-stain negative, aerobic, non-motile, rod-shaped bacterial strains, Y1R2-4T, Y3R2-3 and DC2N1-10T, isolated from two crater lakes of the Daxinganling Mountains, northern China, were studied to determine their taxonomic position. They grew at 4-30 °C (optimally at 20-25 °C), at pH 6.0-7.5 (optimally at pH 7.0) and in the presence of 0-0.5 % (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, these strains showed 95.3-96.6 % similarity to members of the genus Pseudorhodobacter, including Pseudorhodobacter ferrugineus DSM 5888T, Pseudorhodobacter wandonensis WT-MW11T, Pseudorhodobacter antarcticus ZS3-33T and Pseudorhodobacter aquimaris HDW-19T. All strains contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The main polar lipids for strains Y1R2-4T and Y3R2-3 were phosphatidylglycerol, phosphatidylcholine, one unidentified aminophospholipid, one unidentified aminolipid, three unidentified phospholipids and two unidentified lipids, and those for strain DC2N1-10T were phosphatidylglycerol, phosphatidylcholine, one unidentified aminophospholipid, one unidentified aminolipid, one unidentified phospholipid and several unidentified lipids. The DNA G+C contents of strains Y1R2-4T, Y3R2-3 and DC2N1-10T were 61.9, 61.0 and 60.0 mol%, respectively. In addition, strain Y1R2-4T shared less than 50 % DNA-DNA relatedness to strain DC2N1-10T. Based on these differences in genetic, physiological and chemotaxonomic properties, strains Y1R2-4T, Y3R2-3 and DC2N1-10T were considered to represent two novel species of the genus Pseudorhodobacter, for which the names Pseudorhodobacter sinensis sp. nov. (type strain Y1R2-4T=CGMCC1.14435T=KCTC 52039T) and Pseudorhodobacter aquaticus sp. nov. (type strain DC2N1-10T=CGMCC1.14433T=KCTC 52040T) are proposed. PMID:27045957

  1. Pseudorhodobacter sinensis sp. nov. and Pseudorhodobacter aquaticus sp. nov., isolated from crater lakes.

    PubMed

    Li, Ai-Hua; Liu, Hong-Can; Hou, Wei-Guo; Zhou, Yu-Guang

    2016-08-01

    Three Gram-stain negative, aerobic, non-motile, rod-shaped bacterial strains, Y1R2-4T, Y3R2-3 and DC2N1-10T, isolated from two crater lakes of the Daxinganling Mountains, northern China, were studied to determine their taxonomic position. They grew at 4-30 °C (optimally at 20-25 °C), at pH 6.0-7.5 (optimally at pH 7.0) and in the presence of 0-0.5 % (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, these strains showed 95.3-96.6 % similarity to members of the genus Pseudorhodobacter, including Pseudorhodobacter ferrugineus DSM 5888T, Pseudorhodobacter wandonensis WT-MW11T, Pseudorhodobacter antarcticus ZS3-33T and Pseudorhodobacter aquimaris HDW-19T. All strains contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The main polar lipids for strains Y1R2-4T and Y3R2-3 were phosphatidylglycerol, phosphatidylcholine, one unidentified aminophospholipid, one unidentified aminolipid, three unidentified phospholipids and two unidentified lipids, and those for strain DC2N1-10T were phosphatidylglycerol, phosphatidylcholine, one unidentified aminophospholipid, one unidentified aminolipid, one unidentified phospholipid and several unidentified lipids. The DNA G+C contents of strains Y1R2-4T, Y3R2-3 and DC2N1-10T were 61.9, 61.0 and 60.0 mol%, respectively. In addition, strain Y1R2-4T shared less than 50 % DNA-DNA relatedness to strain DC2N1-10T. Based on these differences in genetic, physiological and chemotaxonomic properties, strains Y1R2-4T, Y3R2-3 and DC2N1-10T were considered to represent two novel species of the genus Pseudorhodobacter, for which the names Pseudorhodobacter sinensis sp. nov. (type strain Y1R2-4T=CGMCC1.14435T=KCTC 52039T) and Pseudorhodobacter aquaticus sp. nov. (type strain DC2N1-10T=CGMCC1.14433T=KCTC 52040T) are proposed.

  2. Genomic signatures of divergent selection and speciation patterns in a 'natural experiment', the young parallel radiations of Nicaraguan crater lake cichlid fishes.

    PubMed

    Kautt, Andreas F; Elmer, Kathryn R; Meyer, Axel

    2012-10-01

    Divergent selection is the main driving force in sympatric ecological speciation and may also play a strong role in divergence between allopatric populations. Characterizing the genome-wide impact of divergent selection often constitutes a first step in unravelling the genetic bases underlying adaptation and ecological speciation. The Midas cichlid fish (Amphilophus citrinellus) species complex in Nicaragua is a powerful system for studying evolutionary processes. Independent colonizations of isolated young crater lakes by Midas cichlid populations from the older and great lakes of Nicaragua resulted in the repeated evolution of adaptive radiations by intralacustrine sympatric speciation. In this study we performed genome scans on two repeated radiations of crater lake species and their great lake source populations (1030 polymorphic AFLPs, n ∼ 30 individuals per species). We detected regions under divergent selection (0.3% in the crater lake Xiloá flock and 1.7% in the older crater lake Apoyo radiation) that might be responsible for the sympatric diversifications. We find no evidence that the same genomic regions have been involved in the repeated evolution of parallel adaptations across crater lake flocks. However, there is some genetic parallelism apparent (seven out of 51 crater lake to great lake outlier loci are shared; 13.7%) that is associated with the allopatric divergence of both crater lake flocks. Interestingly, our results suggest that the number of outlier loci involved in sympatric and allopatric divergence increases over time. A phylogeny based on the AFLP data clearly supports the monophyly of both crater lake species flocks and indicates a parallel branching order with a primary split along the limnetic-benthic axis in both radiations.

  3. Summit crater lake observations, and the location, chemistry, and pH of water samples near Mount Chiginagak volcano, Alaska: 2004-2012

    USGS Publications Warehouse

    Schaefer, Janet R.; Scott, William E.; Evans, William C.; Wang, Bronwen; McGimsey, Robert G.

    2013-01-01

    Mount Chiginagak is a hydrothermally active volcano on the Alaska Peninsula, approximately 170 km south–southwest of King Salmon, Alaska (fig. 1). This small stratovolcano, approximately 8 km in diameter, has erupted through Tertiary to Permian sedimentary and igneous rocks (Detterman and others, 1987). The highest peak is at an elevation of 2,135 m, and the upper ~1,000 m of the volcano are covered with snow and ice. Holocene activity consists of debris avalanches, lahars, and lava flows. Pleistocene pyroclastic flows and block-and-ash flows, interlayered with andesitic lava flows, dominate the edifice rocks on the northern and western flanks. Historical reports of activity are limited and generally describe “steaming” and “smoking” (Coats, 1950; Powers, 1958). Proximal tephra collected during recent fieldwork suggests there may have been limited Holocene explosive activity that resulted in localized ash fall. A cluster of fumaroles on the north flank, at an elevation of ~1,750 m, commonly referred to as the “north flank fumarole” have been emitting gas throughout historical time (location shown in fig. 2). The only other thermal feature at the volcano is the Mother Goose hot springs located at the base of the edifice on the northwestern flank in upper Volcano Creek, at an elevation of ~160 m (fig. 2, near sites H1, H3, and H4). Sometime between November 2004 and May 2005, a ~400-m-wide, 100-m-deep lake developed in the snow- and ice-filled summit crater of the volcano (Schaefer and others, 2008). In early May 2005, an estimated 3 million cubic meters (3×106 m3) of sulfurous, clay-rich debris and acidic water exited the crater through tunnels at the base of a glacier that breaches the south crater rim. More than 27 km downstream, these acidic flood waters reached approximately 1.3 m above normal water levels and inundated a fertile, salmon-spawning drainage, acidifying the entire water column of Mother Goose Lake from its surface waters to its

  4. Genetic linkage of distinct adaptive traits in sympatrically speciating crater lake cichlid fish.

    PubMed

    Fruciano, Carmelo; Franchini, Paolo; Kovacova, Viera; Elmer, Kathryn R; Henning, Frederico; Meyer, Axel

    2016-09-06

    Our understanding of how biological diversity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically diverging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits diverge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid divergence in sympatry.

  5. Genetic linkage of distinct adaptive traits in sympatrically speciating crater lake cichlid fish.

    PubMed

    Fruciano, Carmelo; Franchini, Paolo; Kovacova, Viera; Elmer, Kathryn R; Henning, Frederico; Meyer, Axel

    2016-01-01

    Our understanding of how biological diversity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically diverging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits diverge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid divergence in sympatry. PMID:27597183

  6. Genetic linkage of distinct adaptive traits in sympatrically speciating crater lake cichlid fish

    PubMed Central

    Fruciano, Carmelo; Franchini, Paolo; Kovacova, Viera; Elmer, Kathryn R.; Henning, Frederico; Meyer, Axel

    2016-01-01

    Our understanding of how biological diversity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically diverging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits diverge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid divergence in sympatry. PMID:27597183

  7. Multiple isotopic components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Gunn, S.H.; Lanphere, M.A.; Wooden, J.L.

    1994-01-01

    Quaternary lavas and pyroclastic rocks of Mount Mazama, Crater lake caldera, and the surrounding area have variable Sr, Nd, and Pb isotopic compositions. High-alumina olivine tholeiites have 87Ar/86Ar ratios of 0.70346-0.70364; basaltic andesite, 0.70349-0.70372; shoshonitic basaltic andesite, 0.70374-0.70388; and andesite, 0.70324-0.70383. Dacites of Mount Mazama have 87Sr/ 86Sr ratios of 0.70348-0.70373. Most rhyodacites converge on 0.7037. Andesitic to mafic-cumulate scoriae of the climatic eruption, and enclaves in pre-climactic rhyodacites, cluster in two groups but show nearly the entire 87Sr/86Sr range of the data set, confirming previously suggested introduction of diverse parental magmas into the growing climactic chamber. Magma evolution is described. -from Authors

  8. Amino acids in the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Kminek, G.; Botta, O.; Glavin, D. P.; Bada, J. L.

    2002-01-01

    High-performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and CI carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the CI Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated fiom a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P- or D-type asteroids. If the Tagish Lake meteorite was indeed derived fiom these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.

  9. Monitoring direct and indirect climate effects on whitebark pine ecosystems at Crater Lake National park

    USGS Publications Warehouse

    Smith, S.B.; Odion, D.C.; Sarr, D.A.; Irvine, K.M.

    2011-01-01

    Whitebark pine (Pinus albicaulis) is the distinctive, often stunted, and picturesque tree line species in the American West. As a result of climate change, mountain pine beetles (Dendroctonus ponderosae) have moved up in elevation, adding to nonnative blister rust (Cronartium ribicola) disease as a major cause of mortality in whitebark pine. At Crater Lake National Park, Oregon, whitebark pine is declining at the rate of 1% per year. The Klamath Network, National Park Service, has elected to monitor whitebark pine and associated high-elevation vegetation. This program is designed to sample whitebark pine throughout the park to look for geographic patterns in its exposure to and mortality from disease and beetles. First-year monitoring has uncovered interesting patterns in blister rust distribution. Incidence of rust disease was higher on the west side of the park, where conditions are wetter and more humid than on the east side. However, correlating climate alone with rust disease is not straightforward. On the east side of the park, the odds of blister rust infection were much greater in plots having Ribes spp., shrubs that act as the alternate host for a portion of the rust's life cycle. However, on the park's west side, there was not a statistically significant increase in blister rust in plots with Ribes. This suggests that different species of Ribes associated with whitebark pine can increase pine exposure to blister rust disease. There is also convincing evidence of an association between total tree density and the incidence of blister rust. Warmer temperatures and possibly increased precipitation will affect both whitebark pine and Ribes physiology as well as tree density and mountain pine beetle numbers, all of which may interact with blister rust to cause future changes in tree line communities at Crater Lake. The Klamath Network monitoring program plans to document and study these ongoing changes.

  10. Lake evolution during the Early Danian Dan-C2 hyperthermal, Boltysh impact crater, Ukraine

    NASA Astrophysics Data System (ADS)

    Ebinghaus, Alena; Jolley, David W.

    2016-04-01

    Lacustrine facies record complex relationships between lake evolution and environmental conditions and provide proxies for climate changes. However, lacustrine successions formed during past hyperthermals as recorded from negative carbon isotope excursions (CIEs) are of limited availability and thus less well understood. Here, we present a complete lacustrine record of the Early Danian Dan-C2 hyperthermal at c. 65.2 Ma from a core drilled in the K-Pg Boltysh impact crater, Ukraine. This borehole allows a detailed facies analysis and reconstruction of lake evolution and associated plant ecosystem in correspondence with rapid climate change. The Boltysh borehole reveals a c. 400 m thick siliciclastic and organic-rich succession overlying impact melt-breccia dated at 65.17 ± 0.64 Ma. Based on detailed core logging, 8 distinctive facies associations are identified, including 1) littoral mudstones, 2) siliciclastic shoreline deposits, 3) siliciclastic littoral to sublittoral deposits, 4) mudstone laminites, 5) organic-rich mudstones, and deposits of 6) coarse-grained, 7) fine-grained density currents, and 8) debris flows. Based on the occurrence of these facies associations 3 major phases of lake evolution are distinguished: 1) an initial pre-CIE rising clastic-dominated lake phase characterised by the presence of coarse-grained density and debris flow deposits, 2) an organic-rich fluctuating shallow lake phase during the main phase of the CIE, characterised by alternating packages of the mudstone laminites and organic-rich mudstones; and 3) a rising clastic-dominated lake during and post-CIE recovery phase, which shows a high presence of siliciclastic shoreline and littoral to sublittoral deposits. This study provides a full record of lacustrine response to climate change during the Dan-C2 hyperthermal, and subsequently allows us to infer lake formation and environmental conditions at different stages during climate warming. The high resolution sedimentary record

  11. Acid lakes from natural and anthropogenic causes

    SciTech Connect

    Patrick, R.; Binetti, V.P.; Halterman, S.G.

    1981-01-30

    Lakes may be acid because of natural ecological conditions or because of anthropogenic activities. Apparently there has been a recent increase in acidity of many lakes in the northeastern United States. Factors that may be contributing to this increase include the use by utilities of precipitators, sulfur scrubbers, and tall stacks; the use of petroleum; and methods of combustion of fossil fuels.

  12. Geochemistry of the Albano and Nemi crater lakes in the volcanic district of Alban Hills (Rome, Italy)

    NASA Astrophysics Data System (ADS)

    Carapezza, M. L.; Lelli, M.; Tarchini, L.

    2008-12-01

    Lake Albano, located 20 km to the SE of Rome, is hosted within the most recent crater of the quiescent Alban Hills volcanic complex that produced hydromagmatic eruptions in Holocene times. Stratigraphic, archaeological and historical evidence indicates that the lake level underwent important variations in the Bronze Age. Before the IV century B.C. several lahars were generated by water overflows from the lake and in the IV century B.C. Romans excavated a drainage tunnel. The lake is located above a buried carbonate horst that contains a pressurized medium-enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly CO 2. Previous studies recognized the presence of gas emissions also from the crater bottom. In 1997 the possibility of a Nyos-type event triggered by a lake rollover was considered very low, because the CO 2 water concentration at depth was found to be far from saturation. However, considering the high population density nearby, the Italian Civil Protection Department recommended that periodical monitoring be carried out. To this scope we initiated in 2001 a systematic geochemical study of the lake. Thirteen vertical profiles have been repeatedly carried out in 2001-2006, especially in the deepest part of the lake (167 m in 2006), measuring T, pH, dissolved O 2 and electrical conductivity. Water samples were collected from various depths and chemically and isotopically analysed. Two similar profiles have been measured also in the nearby Nemi crater lake. Results indicate that in the 4.5 years of monitoring the pressure of gas dissolved in the Lake Albano deep waters remained much lower than the hydrostatic pressure. A CO 2 soil survey carried out on the borders of the two lakes, indicates the presence of some zones of anomalous degassing of likely magmatic origin. A water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003-2004, when cold rainfall cooled the

  13. Breccia Formation at a Complex Impact Crater: Slate Islands, Lake Superior, Ontario, Canada

    NASA Technical Reports Server (NTRS)

    Dressler, B. O.; Sharpton, V. L.

    1997-01-01

    The Slate Islands impact structure is the eroded remnant of a approximately 30-32 km-diameter complex impact structure located in northern Lake Superior, Ontario, Canada. Target rocks are Archean supracrustal and igneous rocks and Proterozoic metavolcanics, metasediments, and diabase. A wide variety of breccias occurs on the islands, many of which contain fragments exhibiting shock metamorphic features. Aphanitic, narrow and inclusion-poor pseudotachylite veins, commonly with more or less parallel boundaries and apophyses branching off them, represent the earliest breccias formed during the compression stage of the impact process. Coarse-grained, polymictic elastic matrix breccias form small to very large, inclusion-rich dikes and irregularly shaped bodies that may contain altered glass fragments. These breccias have sharp contacts with their host rocks and include a wide range of fragment types some of which were transported over minimum distances of approximately 2 km away from the center of the structure. They cut across pseudotachylite veins and contain inclusions of them. Field and petrographic evidence indicate that these polymictic breccias formed predominantly during the excavation and central uplift stages of the impact process. Monomictic breccias, characterized by angular fragments and transitional contacts with their host rocks, occur in parautochthonous target rocks, mainly on the outlying islands of the Slate Islands archipelago. A few contain fragmented and disrupted, coarse-grained, polymictic clastic matrix breccia dikes. This is an indication that at least some of these monomictic breccias formed late in the impact process and that they are probably related to a late crater modification stage. A small number of relatively large occurrences of glass-poor, suevitic breccias occur at the flanks of the central uplift and along the inner flank of the outer ring of the Slate Islands complex crater. A coarse, glass-free, allogenic breccia, containing

  14. Vernal Crater, SW Arabia Terra: MSL Candidate with Extensively Layered Sediments, Possible Lake Deposits, and a Long History of Subsurface Ice

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Allen, Carlton C.

    2007-01-01

    Vernal Crater is a Mars Science Laboratory (MSL) landing site candidate providing relatively easy access to extensively layered sediments as well as potential lake deposits. Sediments of Vernal Crater are 400-1200 m below those being investigated by Opportunity in Meridiani Planum, and as such would allow study of significantly older geologic units, if Vernal Crater were selected for MSL. The location of Vernal Crater in SW Arabia Terra provides exceptional scientific interest, as rampart craters and gamma-ray spectrometer (GRS) data from the region suggest a long history of ice/fluids in the subsurface. The potential value of this MSL candidate is further enhanced by reports of atmospheric methane over Arabia, as any insight into the source of that methane would significantly increase our understanding of Mars. Finally, should MSL survive beyond its prime mission, the gentle slope within Vernal Crater would provide a route out of the crater for study of the once ice/fluid-rich plains.

  15. High spatio-temporal resolution observations of crater-lake temperatures at Kawah Ijen volcano, East Java, Indonesia

    USGS Publications Warehouse

    Lewicki, Jennifer L.; Corentin Caudron,; Vincent van Hinsberg,; George Hilley,

    2016-01-01

    The crater lake of Kawah Ijen volcano, East Java, Indonesia, has displayed large and rapid changes in temperature at point locations during periods of unrest, but measurement techniques employed to-date have not resolved how the lake’s thermal regime has evolved over both space and time. We applied a novel approach for mapping and monitoring variations in crater-lake apparent surface (“skin”) temperatures at high spatial (~32 cm) and temporal (every two minutes) resolution at Kawah Ijen on 18 September 2014. We used a ground-based FLIR T650sc camera with digital and thermal infrared (TIR) sensors from the crater rim to collect (1) a set of visible imagery around the crater during the daytime and (2) a time series of co-located visible and TIR imagery at one location from pre-dawn to daytime. We processed daytime visible imagery with the Structure-from-Motion photogrammetric method to create a digital elevation model onto which the time series of TIR imagery was orthorectified and georeferenced. Lake apparent skin temperatures typically ranged from ~21 to 33oC. At two locations, apparent skin temperatures were ~ 4 and 7 oC less than in-situ lake temperature measurements at 1.5 and 5 m depth, respectively. These differences, as well as the large spatio-temporal variations observed in skin temperatures, were likely largely associated with atmospheric effects such as evaporative cooling of the lake surface and infrared absorption by water vapor and SO2. Calculations based on orthorectified TIR imagery thus yielded underestimates of volcanic heat fluxes into the lake, whereas volcanic heat fluxes estimated based on in-situ temperature measurements (68 to 111 MW) were likely more representative of Kawah Ijen in a quiescent state. The ground-based imaging technique should provide a valuable tool to continuously monitor crater-lake temperatures and contribute insight into the spatio-temporal evolution of these temperatures associated with volcanic activity.

  16. Acid deposition: Processes of Lake Acidification

    SciTech Connect

    Not Available

    1984-01-01

    The Panel on Processes of Lake Acidification was assembled by the National Research Council at the request of the Environmental Protection Agency. The panel was charged with discussing the processes that control the rate of acidification of streams and lakes and to suggest how EPA's research program might approach addressing current deficiencies in knowledge. The panel defined the acidification of lakes and streams as a decrease in alkalinity over time. Soil acidification is the decrease in the percent base saturation over time. The panel concurred that in forested watersheds that are underlain by granitic or other highly siliceous bedrock with acidic forest soils not receiving appreciable acid deposition, most lakes and streams have bicarbonate as the dominant anion and pH levels above 5.5. Generally, lakes and streams in similar habitats but in areas receiving appreciable acid deposition have sulfate as the dominant anion.

  17. Temporal evolution of micro-eruptions within the crater lake of White Island (Whakaari) during January/February 2013

    NASA Astrophysics Data System (ADS)

    Edwards, Matt; Kennedy, Ben; Jolly, Art; Scheu, Bettina; Taddeucci, Jacopo; Jousset, Philippe; Schmid, Di

    2015-04-01

    Micro-eruptions are potentially modulated by hydrothermal systems and crater lakes but to date have not been well studied. In January/February 2013 White Island (Whakaari), New Zealand, experienced an about three week long period of atypical, frequent micro-eruptions within its crater lake. Many of these micro-eruptions were recorded by tour operators and GNS personnel monitoring the lake activity. Analysis of this video footage reveals an increasingly energetic eruption style. Deformation of the muddy lake surface by ascending bubbles begins as irregularly shaped bursts, producing liquid strings of mud ejected to heights of less than 10m at 10-15m/s. As the episode progresses, eruption frequency is maintained at semi-regular <10s intervals. Each eruption however starts with an increasingly hemispheric surface deformation ~6m in diameter, and bursts occur as "star-bursts" with ejection of less fluidal ash/mud clots. In addition, these bursts are commonly followed within 2s by a more vertical and energetic secondary ejection of material, which occasionally ejects through the deformed hemispheric surface up to >100m high, and reaches ejection velocities up to 45m/s. The period of frequent "star-bursts" is then followed by a two day phase of constant ~30-75m high ash ejection resulting in the formation of a tuff cone with a central open conduit of 6m within the former crater lake. We theorise that this behaviour is influenced by evolving bubble overpressure/volume, including the presence or absence of a trailing wake of smaller bubbles and is modulated over the eruption episode by the viscosity of the crater lake. In the early stages of the episode a lower viscosity lake provides little resistance to rising gas/ash mixtures. Bubble coalescence and/or overpressure development is therefore minimised, resulting in low energy bursts. Over the course of this episode the viscosity of the lake increases due to addition of ash from ash-carrying gas flux and fluid loss by

  18. Water in the Oceanic Lithosphere: Salt Lake Crater Xenoliths, Oahu, Hawaii

    NASA Technical Reports Server (NTRS)

    Peslier, Anne H.; Bizimis, Michael

    2010-01-01

    Water can be present in nominally anhydrous minerals of peridotites in the form of hydrogen bonded to structural oxygen. Such water in the oceanic upper mantle could have a significant effect on its physical and chemical properties. However, the water content of the MORB source has been inferred indirectly from the compositions of basalts. Direct determinations on abyssal peridotites are scarce because they have been heavily hydrothermally altered. Here we present the first water analyses of minerals from spinel peridotite xenoliths of Salt Lake Crater, Oahu, Hawaii, which are exceptionally fresh. These peridotites are thought to represent fragments of the Pacific oceanic lithosphere that was refertilized by alkalic Hawaiian melts. A few have unradiogenic Os and radiogenic Hf isotopes and may be fragments of an ancient (2 Ga) depleted and recycled lithosphere. Water contents in olivine (Ol), orthopyroxene (Opx), and clinopyroxene (Cpx) were determined by FTIR spectrometry. Preliminary H_{2}O contents show ranges of 8-10 ppm for Ol, 151-277 ppm for Opx, and 337-603 ppm for Cpx. Reconstructed bulk rock H_{2}O contents range from 88-131 ppm overlapping estimates for the MORB source. Water contents between Ol minerals of the same xenolith are heterogeneous and individual OH infrared bands vary within a mineral with lower 3230 cm^{-1} and higher 3650-3400 cm^{-1} band heights from core to edge. This observation suggests disturbance of the hydrogen in Ol likely occurring during xenolith entrainment to the surface. Pyroxene water contents are higher than most water contents in pyroxenes from continental peridotite xenoliths and higher than those of abyssal peridotites. Cpx water contents decrease with increasing degree of depletion (e.g. increasing Fo in Ol and Cr# in spinel) consistent with an incompatible behavior of water. However Cpx water contents also show a positive correlation with LREE/HREE ratios and LREE concentrations consistent with refertilization. Opx water

  19. Acid Raindrops Keep Fallin' in My Lake.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 2003

    2003-01-01

    Demonstrates acid rain falling into lakes using vinegar and explores the effects on different types of solids such as chalk, sand, and lime. Includes instructor information and student worksheets. (YDS)

  20. Sequence and relative timing of large lakes in Gale crater (Mars) after the formation of Mount Sharp

    NASA Astrophysics Data System (ADS)

    Palucis, Marisa C.; Dietrich, William E.; Williams, Rebecca M. E.; Hayes, Alexander G.; Parker, Tim; Sumner, Dawn Y.; Mangold, Nicolas; Lewis, Kevin; Newsom, Horton

    2016-03-01

    The quantification of lake levels in Gale crater is important to define the hydrologic and climatic history experienced by the sedimentary deposits found by Curiosity. We propose that there were at least three major lake stands within Gale, each persisted >1000 years, and all occurred after Mount Sharp reached close to its current topographic form. Deltaic deposits off the southern rim of Gale, derived from incision of Farah Vallis, and corresponding deposits off the southern flank of Mount Sharp define the highest lake level, which had a mean depth of 700 m. Canyons similar in form to Farah Vallis enter into craters and/or the crustal dichotomy near Gale from the south, suggesting that the highest lake was supplied by a large-scale flow system. The next lake level, established after a period of drying and rewetting, is defined by four deltaic features, three sourced from Mount Sharp and one from the western rim of Gale, as well as the termination of gullies around the northern rim of Gale. This second lake level had a mean depth of 300 m. The presence of the gullies suggests more locally sourced water. Lake levels then rose another 100 m, as evidenced by two deltaic deposits derived from the rim of Gale and the termination of a second set of gullies. Post-lake, reduced hydrologic activity continued, evidenced by a time of fan building (including Peace Vallis). The sequence of events suggests an episodic shift through time from relatively wet regional conditions to a drier environment with local runoff.

  1. Late Pleistocene granodiorite beneath Crater Lake caldera, Oregon, dated by ion microprobe

    USGS Publications Warehouse

    Bacon, C.R.; Persing, H.M.; Wooden, J.L.; Ireland, T.R.

    2000-01-01

    Variably melted granodiorite blocks ejected during the Holocene caldera-forming eruption of Mount Mazama were plucked from the walls of the climactic magma chamber ~15 km depth. Ion-microprobe U-Pb dating of zircons from two unmelted granodiorite blocks with SHRIMP RG (sensitive high-resolution ion microprobe-reverse geometry) gives a nominal 238U/206Pb age of 101+78-80 ka, or 174+89-115 ka when adjusted for an initial 230Th deficit. SHRIMP RG U-Th measurements on a subset of the zircons yield a 230Th/238U isochron age of 112 ?? 24 ka, considered to be the best estimate of the time of solidification of the pluton. These results suggest that the granodiorite is related to andesite and dacite of Mount Mazama and not to magmas of the climactic eruption. The unexposed granodiorite has an area of at least 28 km2. This young, shallow pluton was emplaced in virtually the same location where a similarly large magma body accumulated and powered violent explosive eruptions ~7700 yr ago, resulting in collapse of Crater Lake caldera.

  2. Analytical laboratory comparison of major and minor constituents in an active crater lake

    NASA Astrophysics Data System (ADS)

    Takano, B.; Fazlullin, S. M.; Delmelle, P.

    2000-04-01

    The crater lake water from Maly Semiachik volcano in Kamchatka was used for the international analytical laboratory comparison of major and minor elements, and hydrogen, sulfur, and oxygen isotope data. Eight institutions participated in this program, giving analytical results of 9 major and 20 minor elements mainly by using ICP-AES for cations and IC for anions. Among the major elements, Na, Mg and Si showed coefficients of variation (CV) of 10% or more, whereas B, Al, Fe, Mn had coefficients less than 7%. The CV% of the minor elements Co, Cu, P, Cr, Pb was much greater (>30%) while the V analyses agreed well (<10%). Ti, Sr, Zn, and F were intermediate (between 10 and 20 CV%). The errors observed for these constituents are inherent to the methods applied: large dilutions and spectrometric interferences. Even the major anions such as Cl (>2000 ppm) and SO 4 (>5000 ppm) gave considerable ranges (5.1 and 8.8 CV%, respectively) as did the obtained pH values (22 CV%). The measured δ18O of the water samples and δ34S of sulfate are in excellent agreement but the δD values had CV% of 8. Technical recommendations are presented to improve the analytical results for these elements with significant deviations from the mean values.

  3. Deformation of the Wineglass Welded Tuff and the timing of caldera collapse at Crater Lake, Oregon

    USGS Publications Warehouse

    Kamata, H.; Suzuki-Kamata, K.; Bacon, C.R.

    1993-01-01

    Four types of deformation occur in the Wineglass Welded Tuff on the northeast caldera rim of Crater Lake: (a) vertical tension fractures; (b) ooze-outs of fiamme: (c) squeeze-outs of fiamme; and (d) horizontal pull-apart structures. The three types of plastic deformation (b-d) developed in the lower part of the Wineglass Welded Tuff where degree of welding and density are maximum. Deformation originated from concentric normal faulting and landsliding as the caldera collapsed. The degree of deformation of the Wineglass Welded Tuff increases toward the northeast part of the caldera, where plastic deformation occurred more easily because of a higher emplacement temperature probably due to proximity to the vent. The probable glass transition temperature of the Wineglass Welded Tuff suggests that its emplacement temperature was ???750??C where the tuff is densely welded. Calculation of the conductive cooling history of the Wineglass Welded Tuff and the preclimactic Cleetwood (lava) flow under assumptions of a initially isothermal sheet and uniform properties suggests that (a) caldera collapse occurred a maximum of 9 days after emplacement of the Wineglass Welded Tuff, and that (b) the period between effusion of the Cleetwood (lava) flow and onset of the climactic eruption was <100 years. If cooling is controlled more by precipitation during quiescent periods than by conduction, these intervals must be shorter than the calculated times. ?? 1993.

  4. On Limnocytherina axalapasco, a new freshwater ostracod (Podocopida: Limnocytheridae) from Mexican crater lakes.

    PubMed

    Cohuo-Durán, Sergio; Pérez, Liseth; Karanovic, Ivana

    2014-03-01

    Limnocytherina is a genus conformed by 12 species; its distribution in the American continent is known to be exclusively on the North (neartics), but little is reported about its distribution from Mexico (transition zone) and Central America (Neotropics). Different sampling campaigns were undertaken in three crater lakes from the Axalapascos region in east-central Mexico, during 2008, 2009 and 2011. As a product of these campaings, the new species of Limnocytherina axalapasco was found, which displays some intraspecific variability among populations. In this study, we described the taxonomy, the habitat, the ecological preferences and the larval development of this new species. A total of 10 sediment samples (8 littoral, 2 deepest point) were collected from lakes Alchichica, La Preciosa and Quechulac. We found that L. axalapasco is closely related to two North American species: L. posterolimba and L. itasca as well as one Central American species L. royi comb. nov. With the inclusion of L. axalapasco and L. royi to the genus, the distribution of Limnocytherina is extended to Central America. The four most important distinguishing characters of this new species are: 1) valve surface and margins covered with small, spine-like projections; 2) most of the A1 setae with a highly developed setule at distal part, producing a bifurcate appearance; 3) the upper ramus on the hemipenis is elongated, and by far overpasses dorsal/distal margins, distal lobe is triangular and short, while the hook-like process is prominent, outward orientated, and overpassing the tip of the distal lobe; 4) the UR is moderately developed with seta f3 elongated and setae f1 and f2 short. Considering its ecological characteristics and larval development, L. axalapasco was preferably found in alkaline waters dominated by Cl(-) or HCO3(-) and Na+ or Mg2+, temperatures ranging between 19.1 to 20.3 degrees C, and dissolved oxygen concentrations from 5 to 6.5 mg/L. This species was abundant in deeper

  5. Digital Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

    NASA Astrophysics Data System (ADS)

    Bacon, C. R.; Ramsey, D. W.

    2002-12-01

    Crater Lake caldera formed ~7700 cal yr B.P. by the eruption of 50 km3 of mainly rhyodacitic magma and the resulting collapse of Mount Mazama. A new 1:24,000-scale digital geologic map compiled in ArcInfo depicts the geology of this volcanic center, peripheral volcanoes, the caldera walls and floor, and superjacent pyroclastic, talus, and glacial deposits. The geology of the caldera walls was mapped in the field on photographs taken from the lake (see accompanying abstract and poster, "Geologic panoramas of the walls of Crater Lake caldera,Oregon"); the geology of the flanks of Mount Mazama and the surrounding area was mapped on aerial photographs; and features of the caldera floor were mapped on a multibeam echo-sounding bathymetric map (Gardner et al., 2001; Bacon et al., 2002). Volcanic map units are defined on the basis of chemical composition and petrographic characteristics. Map unit colors were chosen to indicate the compositions of volcanic rocks, cooler colors for mafic units and warmer colors for silicic units. Map unit color intensity indicates age, with more intense coloring for younger units. Ages of many units have been determined by K-Ar and 40Ar/39Ar dating by M.A. Lanphere. Several undated units have been correlated using paleomagnetic secular variation measurements by D.E. Champion. Crystallization facies of some of the larger lava flows are mapped separately (e.g., vitrophyre, felsite, carapace), as are breccia and lava facies of submerged postcaldera volcanoes. Also shown on the caldera floor are landslide (debris avalanche) and sediment gravity-flow deposits. A major north-south normal fault system traverses the map area west of the caldera and displaces dated late Pleistocene lava flows, allowing determination of a long-term slip rate of ~0.3 mm/yr (Bacon et al., 1999). Faults bounding large downdropped blocks of the south caldera wall are also shown. Where practical, lava flow margins are represented as intra-unit contacts. A number of small

  6. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids.

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-06-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  7. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids.

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-06-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  8. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids

    PubMed Central

    Kautt, Andreas F.; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-01-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  9. Discovery of an Active Microbial Community in a Subglacial Volcanic Crater Lake, Iceland

    NASA Astrophysics Data System (ADS)

    Gaidos, E.; Lanoil, B.; Thorsteinsson, T.; Graham, A.; Skidmore, M.; Decarlo, E.; Popp, B.

    2002-12-01

    Grímsvötn, an active volcano beneath the Vatnajökull glacier in Iceland, hosts a subglacial caldera lake (Gudmundsson, Sigmundsson and Björnsson 1997 Nature 389, 954). Except for earlier geochemical measurements (Ágústsdóttir and Brantley 1994 J. Geophys. Res. 99, 9505), the lake and its possible biota have remained unexplored. In June 2002 we penetrated the 300-meter ice sheet over the lake using hot-water drilling and collected water and tephra sediment samples. The 85oC drilling water and chemical sterilization of equipment were used to minimize sample contamination. Samples of borehole water, glacial ice, and snow were also obtained. Lake water was at the freezing point and samples had no sulfidic smell indicative of anaerobic conditions. One sample from the borehole actively degassed after retrieval. Waters were slightly acidic (pH ≈ 5) and fresh ([Na] = 5 ppm) with low sulfate (2 ppm). Elevated transition metal levels measured by ICP-MS are being analyzed. Direct (DAPI stain) cell counts in water and sediment average 2 x 104 cells ml-1 and 4 x 107 cells ml-1, respectively. Counts on R2A plates incubated under aerobic conditions at 22oC and 6oC for one week were 1-2 x 104 and 5 x 103 CFU/ml, respectively. These values may reflect growth during sample shipment, however, growth at 6oC indicates the presence of psychrophilic or at least psychrotolerant organisms in the lake. Colonies from lake and post-penetration borehole samples were distinct from those of the borehole, ice and snow. Incubations of lake samples at 4oC showed incorporation of 14C (from bicarbonate). Incubations of other aliquots with a nitrogen-acetylene mixture indicated production of ethylene suggestive of nitrogenase activity. DNA will be extracted and analyzed to determine if the microbial community is distinct from that in the overlying snow and ice.

  10. Origin and speciation of haplochromine fishes in East African crater lakes investigated by the analysis of their mtDNA, Mhc genes, and SINEs.

    PubMed

    Sato, Akie; Takezaki, Naoko; Tichy, Herbert; Figueroa, Felipe; Mayer, Werner E; Klein, Jan

    2003-09-01

    The Western Branch of the East African Great Rift Valley is pocketed with craters of extinct or dormant volcanoes. Many of the craters are filled with water, and the lakes are inhabited by fishes. The objective of the present study was to determine the amount and nature of genetic variation in haplochromine fishes inhabiting two of these crater lakes, Lake Lutoto and Lake Nshere, and to use this information to infer the origin and history of the two populations. To this end, sequences of mitochondrial (mt) DNA control region, exon 2 of major histocompatibility complex (Mhc) class II B genes, and short interspersed elements (SINEs) were analyzed. The results indicate that the Lake Nshere and Lake Lutoto fishes originated from different but related large founding populations derived from the Kazinga Channel, which connects Lake Edward and Lake George. Some of the genetic polymorphism that existed in the ancestral populations was lost in the populations of the two lakes. The polymorphism that has been retained has persisted for some 50000 generations (years). During this time, new mutations arose and became fixed in each of the two populations in the mtDNA, giving rise to sets of diagnostic substitutions. Each population evolved in isolation after the colonization of the lakes less than 50000 years ago. There appears to be no population structure within the crater lake fishes, and their present effective population sizes are in the order of 104 to 105 individuals. Comparisons with the endemic haplochromine species of Lake Victoria reveal interesting parallels, as well as differences, which may help to understand the nature of the speciation process.

  11. Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.

    NASA Astrophysics Data System (ADS)

    Bacon, Charles R.

    1983-10-01

    New investigations of the geology of Crater Lake National Park necessitate a reinterpretation of the eruptive history of Mount Mazama and of the formation of Crater Lake caldera. Mount Mazama consisted of a glaciated complex of overlapping shields and stratovolcanoes, each of which was probably active for a comparatively short interval. All the Mazama magmas apparently evolved within thermally and compositionally zoned crustal magma reservoirs, which reached their maximum volume and degree of differentiation in the climactic magma chamber ˜ 7000 yr B.P. The history displayed in the caldera walls begins with construction of the andesitic Phantom Cone ˜ 400,000 yr B.P. Subsequently, at least 6 major centers erupted combinations of mafic andesite, andesite, or dacite before initiation of the Wisconsin Glaciation ˜ 75,000 yr B.P. Eruption of andesitic and dacitic lavas from 5 or more discrete centers, as well as an episode of dacitic pyroclastic activity, occurred until ˜ 50,000 yr B.P.; by that time, intermediate lava had been erupted at several short-lived vents. Concurrently, and probably during much of the Pleistocene, basaltic to mafic andesitic monogenetic vents built cinder cones and erupted local lava flows low on the flanks of Mount Mazama. Basaltic magma from one of these vents, Forgotten Crater, intercepted the margin of the zoned intermediate to silicic magmatic system and caused eruption of commingled andesitic and dacitic lava along a radial trend sometime between ˜ 22,000 and ˜ 30,000 yr B.P. Dacitic deposits between 22,000 and 50,000 yr old appear to record emplacement of domes high on the south slope. A line of silicic domes that may be between 22,000 and 30,000 yr old, northeast of and radial to the caldera, and a single dome on the north wall were probably fed by the same developing magma chamber as the dacitic lavas of the Forgotten Crater complex. The dacitic Palisade flow on the northeast wall is ˜ 25,000 yr old. These relatively silicic

  12. Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.

    USGS Publications Warehouse

    Bacon, C.R.

    1983-01-01

    New investigations of the geology of Crater Lake National Park necessitate a reinterpretation of the eruptive history of Mount Mazama and of the formation of Crater Lake caldera. Mount Mazama consisted of a glaciated complex of overlapping shields and stratovolcanoes, each of which was probably active for a comparatively short interval. All the Mazama magmas apparently evolved within thermally and compositionally zoned crustal magma reservoirs, which reached their maximum volume and degree of differentiation in the climactic magma chamber ??? 7000 yr B.P. The history displayed in the caldera walls begins with construction of the andesitic Phantom Cone ??? 400,000 yr B.P. Subsequently, at least 6 major centers erupted combinations of mafic andesite, andesite, or dacite before initiation of the Wisconsin Glaciation ??? 75,000 yr B.P. Eruption of andesitic and dacitic lavas from 5 or more discrete centers, as well as an episode of dacitic pyroclastic activity, occurred until ??? 50,000 yr B.P.; by that time, intermediate lava had been erupted at several short-lived vents. Concurrently, and probably during much of the Pleistocene, basaltic to mafic andesitic monogenetic vents built cinder cones and erupted local lava flows low on the flanks of Mount Mazama. Basaltic magma from one of these vents, Forgotten Crater, intercepted the margin of the zoned intermediate to silicic magmatic system and caused eruption of commingled andesitic and dacitic lava along a radial trend sometime between ??? 22,000 and ??? 30,000 yr B.P. Dacitic deposits between 22,000 and 50,000 yr old appear to record emplacement of domes high on the south slope. A line of silicic domes that may be between 22,000 and 30,000 yr old, northeast of and radial to the caldera, and a single dome on the north wall were probably fed by the same developing magma chamber as the dacitic lavas of the Forgotten Crater complex. The dacitic Palisade flow on the northeast wall is ??? 25,000 yr old. These relatively

  13. Eruptive history and geochronology of Mount Mazama and the Crater Lake region, Oregon

    USGS Publications Warehouse

    Bacon, Charles R.; Lanphere, Marvin A.

    2006-01-01

    Geologic mapping, K-Ar, and 40Ar/39Ar age determinations, supplemented by paleomagnetic measurements and geochemical data, are used to quantify the Quaternary volcanic history of the Crater Lake region in order to define processes and conditions that led to voluminous explosive eruptions. The Cascade arc volcano known as Mount Mazama collapsed during its climactic eruption of ∼50 km3 of mainly rhyodacitic magma ∼7700 yr ago to form Crater Lake caldera. The Mazama edifice was constructed on a Pleistocene silicic lava field, amidst monogenetic and shield volcanoes ranging from basalt to andesite similar to parental magmas for Mount Mazama. Between 420 ka and 35 ka, Mazama produced medium-K andesite and dacite in 2:1 proportion. The edifice was built in many episodes; some of the more voluminous occurred approximately coeval with volcanic pulses in the surrounding region, and some were possibly related to deglaciation following marine oxygen isotope stages (MIS) 12, 10, 8, 6, 5.2, and 2. Magmas as evolved as dacite erupted many times, commonly associated with or following voluminous andesite effusion. Establishment of the climactic magma chamber was under way when the first preclimactic rhyodacites vented ca. 27 ka. The silicic melt volume then grew incrementally at an average rate of 2.5 km3 k.y.−1 for nearly 20 k.y. The climactic eruption exhausted the rhyodacitic magma and brought up crystal-rich andesitic magma, mafic cumulate mush, and wall-rock granodiorite. Postcaldera volcanism produced 4 km3 of andesite during the first 200–500 yr after collapse, followed at ca. 4800 yr B.P. by 0.07 km3 of rhyodacite. The average eruption rate for all Mazama products was ∼0.4 km3 k.y.−1, but major edifice construction episodes had rates of ∼0.8 km3 k.y.−1. The long-term eruption rate for regional monogenetic and shield volcanoes was d∼0.07 km3 k.y.−1, but only ∼0.02 km3 k.y.−1 when the two major shields are excluded. Plutonic xenoliths and evidence for

  14. Geochemistry of Apatite in Climactic and Pre-Climactic Tephra from Mt. Mazama, Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Mandeville, C. W.; Langstaff, M.

    2007-12-01

    predict that most Mazama apatites in Cleetwood and climactic pumices should contain 0.4 wt.% or more SO3. Most apatites in Cleetwood and climactic rhyodacites contain less than 0.20 wt.% SO3 indicating crystallization from rhyodacitic melt that exsolved a sulfur-rich vapor prior to eruption that drastically reduced melt sulfur concentration. Apatites with SO3 greater than 0.60 wt.% most probably were derived from more mafic oxidized magmas with dissolved sulfur contents of 2000 ppm or more that have been measured in high-Sr andesitic scoria melt inclusions. Mole fraction fluorapatite in Mazama apatites ranges from 0.20 to 0.96 and based on comparison to recent experimental data predicts melt F concentrations of 200 to 1800 ppm that agrees with measured F in melt inclusions of 200 to 1300 ppm. Mole fraction chlorapatite ranges from 0.11 to 0.19 and based on recent experimental data predicts Cl concentrations in rhyodacitic melt of 0.3 to 0.4 wt.% in reasonable agreement with Cl concentrations in melt inclusions ranging from 0.18 to 0.39 wt.%. References Bacon C.R., and Druitt T.H. (1988) Compositional evolution of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon. Contrib. Mineral. Petrol. 98:224-256. Druitt T.H., and Bacon C.R. (1989) Petrology of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon. Contrib. Mineral. Petrol. 101:245-259. Peng G., Luhr J.F. and McGee J.J. (1997) Factors controlling sulfur concentrations in volcanic apatite. Am. Mineral. 82:1210-1224.

  15. Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region.

    PubMed

    Guo, Rui; Reiner, Eric J; Bhavsar, Satyendra P; Helm, Paul A; Mabury, Scott A; Braekevelt, Eric; Tittlemier, Sheryl A

    2012-11-01

    A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78 % to 121 %. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145 ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2 ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045 ± 0.023 ng/g. Mean concentrations of PFOA were not significantly different (p > 0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032 ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.

  16. Multiparameter Monitoring Techniques for Reducing Volcanic Risk from Cuicocha Crater Lake, Ecuador

    NASA Astrophysics Data System (ADS)

    Ruiz, A. G.; Samaniego, P.; von Hillebrandt-Andrade, C.; Hall, M. L.; Ruiz, M. C.; Mothes, P. A.; Macias, C. A.

    2013-05-01

    Cuicocha, a crater-lake volcano located 50 km north of Quito, had an explosive caldera eruption 3000 yBP (Hillebrandt, 1989) that affected an important area of the northern part of the Ecuadorian Interandean valley. The first seismic station was installed at Cuicocha in 1988. Since 2010, this volcano showed an increase of their seismic activity, with several earthquakes felt by inhabitants near the volcano, as well as a subtle increase of the CO2 gas emission. After that, the Instituto Geofisico initiated a program for improving the monitoring capacity combined with a new geological field work dataset. Three broad band stations were installed, two of them outside the caldera rim and the other one, CUIC station, is located just over the Yerovi island dome. Two continuous GPS stations NetRS were installed, one 5 km east of Cuicocha and the other inside the caldera. On Yerovi dome it was deployed a permanent CO2 spectrometer. The Instituto Geofisico carries out a periodically EDM and gas measurements on the volcano in order to correlate geodesic data set and degasing CO2 flux. At the same time, we are re-evaluating the eruptive chronology and the eruptive dynamisms of the Cuicocha caldera eruptions, as well as the petrology of the paroxysmal eruptive products. Preliminary results confirm the 3000 yBP eruption age and our current work will be able to constraint the dynamisms, frequency and size of this paroxysmal eruption of Cuicocha. Finally, we plan to use all this information to re-edit the hazard map (von Hillebrandt and Hall, 1988) and guide local authorities and population to reduce the volcanic risk.

  17. Late Pleistocene granodiorite source for recycled zircon and phenocrysts in rhyodacite lava at Crater Lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Lowenstern, J. B.

    2005-01-01

    Rhyodacite tephra and three lavas erupted ???27 ka, interpreted to be early leaks from the climactic magma chamber of Mount Mazama, contain ubiquitous resorbed crystals (antecrysts) that were recycled from young granodiorite and related plutonic rocks of the same magmatic system. The shallow composite pluton is represented by blocks ejected in the 7.7-ka climactic eruption that formed Crater Lake caldera. Plagioclase crystals in both rhyodacite and granodiorites commonly have cores with crystallographically oriented Fe-oxide needles exsolved at subsolidus conditions. At least 80% of plagioclase crystals in the rhyodacite are antecrysts derived from plutonic rocks. Other crystals in the rhyodacite, notably zircon, also were recycled. SIMS 238U- 230Th dating indicates that zircons in 4 granodiorite blocks crystallized at various times between ???20 ka and ???300 ka with concentrations of analyses near 50-70, ???110, and ???200 ka that correspond to periods of dacitic volcanism dated by K- Ar. U-Th ages of zircon from a rhyodacite sample yield similar results. No analyzed zircons from the granodiorite or rhyodacite are pre-Quaternary. Zircon minimum ages in blocks from different locations around the caldera reflect ages of nearby volcanic vents and may map the distribution of intrusions within a composite pluton. Survival of zircon in zircon-undersaturated hydrous magma and of Fe-oxide needles in plagioclase suggests that little time elapsed from entrainment of antecrysts to the ???27-ka eruption of the rhyodacite. The ???27-ka rhyodacite is an example of young silicic magma that preserved unstable antecrysts from a known source early during growth of a large high-level magma chamber. In contrast, the voluminous 7.7-ka climactic rhyodacite pumice is virtually lacking in zircon, indicating dissolution of any granodioritic debris in the intervening period. Mineralogical evidence of assimilation may be destroyed in hot, vigorously growing silicic magma bodies such as

  18. Seasonal nutrient and plankton dynamics in a physical-biological model of Crater Lake

    USGS Publications Warehouse

    Fennel, K.; Collier, R.; Larson, G.; Crawford, G.; Boss, E.

    2007-01-01

    A coupled 1D physical-biological model of Crater Lake is presented. The model simulates the seasonal evolution of two functional phytoplankton groups, total chlorophyll, and zooplankton in good quantitative agreement with observations from a 10-year monitoring study. During the stratified period in summer and early fall the model displays a marked vertical structure: the phytoplankton biomass of the functional group 1, which represents diatoms and dinoflagellates, has its highest concentration in the upper 40 m; the phytoplankton biomass of group 2, which represents chlorophyta, chrysophyta, cryptomonads and cyanobacteria, has its highest concentrations between 50 and 80 m, and phytoplankton chlorophyll has its maximum at 120 m depth. A similar vertical structure is a reoccurring feature in the available data. In the model the key process allowing a vertical separation between biomass and chlorophyll is photoacclimation. Vertical light attenuation (i.e., water clarity) and the physiological ability of phytoplankton to increase their cellular chlorophyll-to-biomass ratio are ultimately determining the location of the chlorophyll maximum. The location of the particle maxima on the other hand is determined by the balance between growth and losses and occurs where growth and losses equal. The vertical particle flux simulated by our model agrees well with flux measurements from a sediment trap. This motivated us to revisit a previously published study by Dymond et al. (1996). Dymond et al. used a box model to estimate the vertical particle flux and found a discrepancy by a factor 2.5-10 between their model-derived flux and measured fluxes from a sediment trap. Their box model neglected the exchange flux of dissolved and suspended organic matter, which, as our model and available data suggests is significant for the vertical exchange of nitrogen. Adjustment of Dymond et al.'s assumptions to account for dissolved and suspended nitrogen yields a flux estimate that is

  19. Os and U-Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Ankney, Meagan E.; Shirey, Steven B.; Hart, Garret L.; Bacon, Charles R.; Johnson, Clark M.

    2016-03-01

    Interaction of mantle melts with the continental crust can have significant effects on the composition of the resulting melts as well as on the crust itself, and tracing this interaction is key to our understanding of arc magmatism. Lava flows and pyroclastic deposits erupted from ∼50 to 7.7 ka at Mt. Mazama (Crater Lake, Oregon) were analyzed for their Re/Os and U-Th isotopic compositions. Mafic lavas from monogenetic vents around Mt. Mazama that erupted during the buildup to its climactic eruption have lower 187Os/188Os ratios (0.1394 to 0.1956) and high 230Th excess ((230Th/238U)0 of 1.180 to 1.302), whereas dacites and rhyodacites tend to have higher 187Os/188Os ratios (0.2292 to 0.2788) and significant 238U excess ((230Th/238U)0 of 0.975 to 0.989). The less radiogenic Os isotope compositions of the mafic lavas can be modeled by assimilation of young (∼2.5 to 7 Ma), mafic lower crust that was modified during regional extension, whereas the more radiogenic Os isotope compositions of the dacites and rhyodacites can be attributed to assimilation of older (∼10 to 16 Ma), mid to upper crust that acquired its composition during an earlier period of Cascade magmatism. Production of Th excesses in the lower crust requires very young garnet formation accompanying dehydration melting in the lower crust at less than a few 100 ka by heat from recent basaltic magma injection. The results from this study suggest that the combination of Os and Th isotopes may be used to provide insights into the timescales of evolution of the continental crust in arc settings, as well as the influence of the crust on erupted magmas, and suggest a link between the age and composition of the lower and upper crust to regional tectonic extension and/or earlier Cascade magmatism.

  20. Lithic breccia and ignimbrite erupted during the collapse of Crater Lake Caldera, Oregon

    USGS Publications Warehouse

    Druitt, T.H.; Bacon, C.R.

    1986-01-01

    The climactic eruption of Mount Mazama (6845 y.B.P.) vented a total of ???50 km3 of compositionally zoned rhyodacitic to basaltic magma from: (a) a single vent as a Plinian pumice fall deposit and the overlying Wineglass Welded Tuff, and (b) ring vents as ignimbrite and coignimbrite lithic breccia accompanying the collapse of Crater Lake caldera. New field and grain-size data for the ring-vent products are presented in this report. The coarse-grained, poorly bedded, clast-supported lithic breccia extends as far as 18 km from the caldera center. Like the associated ignimbrite, the breccia is compositionally zoned both radially and vertically, and silicic, mixed, and mafic types can be recognized, based on the proportion of rhyodacitic pumice. Matrix fractions in silicic breccias are depleted of fines and are lithic- and crystal-enriched relative to silicic ignimbrite due to vigorous gas sorting during emplacement. Ignimbrite occurs as a proximal veneer deposit overlying the breccia, a medial (??? 8 to ??? 25 km from the caldera center), compositionally zoned valley fill as much as > 110 m thick, and an unzoned distal ({slanted equal to or greater-than} 20 km) facies which extends as far as 55 km from the caldera. Breccia within ??? 9 km of the caldera center is interpreted as a coignimbrite lag breccia formed within the deflation zone of the collapsing ring-vent eruption columns. Expanded pyroclastic flows of the deflation zone were probably vertically graded in both size and concentration of blocks, as recently postulated for some turbidity currents. An inflection in the rate of falloff of lithic-clast size within the lithic breccia at ??? 9 km may mark the outer edge of the deflation zone or may be an artifact of incomplete exposure. The onset of ring-vent activity at Mt. Mazama was accompanied by a marked increase in eruptive discharge. Pyroclastic flows were emplaced as a semicontinuous stream, as few ignimbrite flow-unit boundaries are evident. As eruption from

  1. Structure and physical characteristics of pumice from the climactic eruption of Mount Mazama (Crater Lake), Oregon

    USGS Publications Warehouse

    Klug, C.; Cashman, K.; Bacon, C.

    2002-01-01

    The vesicularity, permeability, and structure of pumice clasts provide insight into conditions of vesiculation and fragmentation during Plinian fall and pyroclastic flow-producing phases of the ???7,700 cal. year B.P. climactic eruption of Mount Mazama (Crater Lake), Oregon. We show that bulk properties (vesicularity and permeability) can be correlated with internal textures and that the clast structure can be related to inferred changes in eruption conditions. The vesicularity of all pumice clasts is 75-88%, with >90% interconnected pore volume. However, pumice clasts from the Plinian fall deposits exhibit a wider vesicularity range and higher volume percentage of interconnected vesicles than do clasts from pyroclastic-flow deposits. Pumice permeabilities also differ between the two clast types, with pumice from the fall deposit having higher minimum permeabilities (???5??10-13 m2) and a narrower permeability range (5-50??10-13 m2) than clasts from pyroclastic-flow deposits (0.2-330??10-13 m2). The observed permeability can be modeled to estimate average vesicle aperture radii of 1-5 ??m for the fall deposit clasts and 0.25-1 ??m for clasts from the pyroclastic flows. High vesicle number densities (???109 cm-3) in all clasts suggest that bubble nucleation occured rapidly and at high supersaturations. Post-nucleation modifications to bubble populations include both bubble growth and coalescence. A single stage of bubble nucleation and growth can account for 35-60% of the vesicle population in clasts from the fall deposits, and 65-80% in pumice from pyroclastic flows. Large vesicles form a separate population which defines a power law distribution with fractal dimension D=3.3 (range 3.0-3.5). The large D.value, coupled with textural evidence, suggests that the large vesicles formed primarily by coalescence. When viewed together, the bulk properties (vesicularity, permeability) and textural characteristics of all clasts indicate rapid bubble nucleation followed by

  2. Distribution of Glycerol Diakyl Glycerol Tetraethers in Surface Soil and Crater Lake Sediments from Mount Kenya, East Africa

    NASA Astrophysics Data System (ADS)

    Omuombo, C.; Huguet, A.; Olago, D.; Williamson, D.

    2013-12-01

    Glycerol diakyl glycerol tetraethers (GDGTs), a palaeoclimate proxy based on the relative abundance of lipids produced by archaea and bacteria, is gaining wide acceptance for the determination of past temperature and pH conditions. This study looks at the spatial distribution and abundance of GDGTs in soil and sediment samples along an altitudinal transect from 3 crater lakes of Mt. Kenya (Lake Nkunga, Sacred Lake and Lake Rutundu) ranging in elevation from 1700m - 3080m above sea level. GDGTs were extracted with solvents and then analysed using high performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS). Mean annual air temperature and pH were estimated based on the relative abundance of the different branched GDGTs, i.e. on the MBT (Methylation index of Branched Tetraethers) and CBT (Cyclization ratio of Branched Tetraethers) indices. Substantial amount of GDGTs were detected in both soil and sediment samples. In addition, branched GDGT distribution was observed to vary with altitude. These results highlight the importance of quantifying the branched GDGTs to understand the environmental parameters controlling the distribution of these lipids. The MBT/CBT proxy is a promising tool to infer palaeotemperatures and characterize the climate events of the past millennia in equatorial east Africa.

  3. Spatial characterization of acid rain stress in Canadian Shield lakes

    NASA Technical Reports Server (NTRS)

    Tanis, Fred J.

    1986-01-01

    The acidification of lake waters from airborne pollutants is of continental proportions both in North America and Europe. A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forest. The number of lakes affected in northeastern United States and on the Canadian Shield is though to be enormous. The principle objective is to examine how seasonal changes in lake water transparency are related to annual acidic load. Further, the relationship between variations in lake acidification and ecophysical units is being examined. Finally, the utility of Thematic Mapper (TM) based observations to measure seasonal changes in the optical transparency in acid lakes is being investigated.

  4. Building a large magma chamber at Mount Mazama, Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Wright, H. M.; Karlstrom, L.; Bacon, C. R.

    2012-12-01

    Crater Lake caldera, Oregon, a structure produced by the 50 km3 eruption of Mount Mazama ~7.7 ka, is one of only three identified Quaternary calderas in the Cascades volcanic chain (Hildreth 2007). What were the conditions necessary to build a large volume magma chamber capable of producing this caldera-forming eruption at Mount Mazama? Using the well-documented >400,000 year volcanic history at Mazama (Bacon and Lanphere 2006), an approximation of vent locations for each eruptive unit (Bacon 2008), and a compilation of over 900 whole-rock compositions from Mount Mazama and regional volcanic rocks, we examine questions of magma chamber assembly in an active volcanic arc. These questions include: (1) is magmatic input approximately constant in composition between Mazama and regional monogenetic volcanic centers? (2) how did melt evolution differ in the two cases (Mazama vs. regional volcanism)? (3) is there spatiotemporal evidence in eruption data (including eruptive volume and chemistry) for a growing magma chamber at depth? and (4) does stability of that chamber require pre-warming of the surrounding country rock? An assumption of approximately constant major-element composition magmatic input is consistent with observed compositional overlap between basaltic to basaltic andesitic eruptive products at Mount Mazama and its vicinity (within 15 km of the volcano). MELTS modeling (Ghiorso and Sack 1995) from an initial composition of magnesian basaltic andesite of monogenetic Red Cone (erupted at a distance of ~8 km from the climactic vent) is consistent with water-saturated magmatic evolution at relatively shallow depths (<500 MPa, with the caveat that shallow pressure calibration data are largely lacking from MELTS models). Within this pressure range, differences in whole-rock compositions indicate that regional magmatic rocks evolved at shallower depths and/or drier conditions than those at the Mazama center. Observations of eruptive ages, compositions, vent

  5. Compositional evolution of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Druitt, T.H.

    1988-01-01

    The climactic eruption of Mount Mazama has long been recognized as a classic example of rapid eruption of a substantial fraction of a zoned magma body. Increased knowledge of eruptive history and new chemical analyses of ???350 wholerock and glass samples of the climactic ejecta, preclimactic rhyodacite flows and their inclusions, postcaldera lavas, and lavas of nearby monogenetic vents are used here to infer processes of chemical evolution of this late Pleistocene - Holocene magmatic system. The 6845??50 BP climactic eruption vented ???50 km3 of magma to form: (1) rhyodacite fall deposit; (2) welded rhyodacite ignimbrite; and (3) lithic breccia and zoned ignimbrite, these during collapse of Crater Lake caldera. Climactic ejecta were dominantly homogeneous rhyodacite (70.4??0.3% SiO2), followed by subordinate andesite and cumulate scoriae (48-61% SiO2). The gap in wholerock composition reflects mainly a step in crystal content because glass compositions are virtually continuous. Two types of scoriae are distinguished by different LREE, Rb, Th, and Zr, but principally by a twofold contrast in Sr content: High-Sr (HSr) and low-Sr (LSr) scoriae. HSr scoriae were erupted first. Trace element abundances indicate that HSr and LSr scoriae had different calcalkaline andesite parents; basalt was parental to some mafic cumulate scoriae. Parental magma compositions reconstructed from scoria wholerock and glass data are similar to those of inclusions in preclimactic rhyodacites and of aphyric lavas of nearby monogenetic vents. Preclimactic rhyodacite flows and their magmatic inclusions give insight into evolution of the climactic chamber. Evolved rhyodacite flows containing LSr andesite inclusions were emplaced between ???30000 and ???25000 BP. At 7015??45 BP, the Llao Rock vent produced a zoned rhyodacite pumice fall, then rhyodacite lava with HSr andesite inclusions. The Cleetwood rhyodacite flow, emplaced immediately before the climactic eruption and compositionally

  6. Distribution of haloacetic acids in the water columns of the Laurentian Great Lakes and Lake Malawi.

    PubMed

    Scott, Brian F; Spencer, Christine; Marvin, Christopher H; MacTavish, David C; Muir, Derek C G

    2002-05-01

    Haloacetic acids (HAAs) are persistent and mildly phytotoxic compounds that have been detected in many aquatic environments, including the waters of the Great Lakes. Sources of HAAs, especially of trifluoroacetic acid (TFA), are not well understood. In this study we assessed the influence of urbanization on the concentrations and profiles of HAAs in the Laurentian Great Lakes and in Lake Malawi, an African Great Lake. Vertical depth profiles for these compounds were taken for each of the Great Lakes with additional profiles taken 2 years later for Lakes Erie and Ontario. The results showed that while TFA was relatively constant throughout the water column, the chloroacetic acids (CAAs) varied with depth. There was a trend of increasing TFA proceeding from Lake Superior to Lake Ontario (18-150 ng/L). Total CAA concentrations were relatively constant throughout the lakes (approximately 500 ng/L) with dichloroacetic acid being the most abundant. No bromoacetic acids were detected. In the Detroit River, a connecting channel between Lakes Huron and Erie, the TFA values were similar to those in Lake Huron, but the CAAs levels were higher than in the upstream lakes and dependent on location, indicating inputs from urban areas along the river. These results were compared to those from Lake Malawi, which has a high population density within the watershed but no heavy industry. CAAs were nondetectable, and TFA concentrations were just at the detection limit (1 ng/L). Total HAA in the water column of Lakes Superior and Huron was compared to annual precipitation inputs at a site situated near both lakes. For Lake Huron, precipitation was a minor contributor to the total HAA inventory of the lake, but for Lake Superior precipitation could be the major contributor to the mass of HAA in this lake. Generally, high HAA levels paralleled the degree of industrial activity in the adjacent waters.

  7. Faults, Post-1720 Explosion Craters, and the Remains of a Lava Lake at Castro Bank Seamount (E Azores)

    NASA Astrophysics Data System (ADS)

    Wunderman, R.; Barriga, F. J.; Nishimura, C.; Pacheco, J. M.; Vogt, P. R.; Gaspar, J. L.; Queiroz, G.; Santos, R.

    2003-12-01

    During 25-28 July 2003 the US Navy submarine NR-1 dove on the seamount D. Joao de Castro Bank, compiling reconnaissance sonar and visual data. Castro Bank sits along strike and between the eastern Azorian islands of Terceira and S. Miguel, occupying a seismically active region ˜60 km from each of these islands and apparently controlled by the same underlying tectonics as other islands found along the Azores' northern margin. Castro Bank's last recorded eruptions built a ˜1 km diameter ephemeral island in the 1720s. The bathimetry of the uppermost 40 m or so of the Bank is rather well known via single beam sonar, scuba diving and AUV surveys (IH, DOP/UA and ISR/IST, unpublished work). Our dives compiled data in concentric rings along contours, collecting side- and forward-looking sonar along an overall track length of ˜20 km, with the deepest ring approaching ˜200 m depth. To document key features we came near the sea floor and took videos in water with typical visibility of ˜10-15 m. This is the first progress report on our work, which found the edifice morphologically complex and irregular. We noted that the seamount was often covered by aerially extensive yellow-brown hyaloclastic tuffs that were presumably products of the 1720s eruption, but also cut by faults and fissures (with offsets of ten's of meters) exposing abundant areas of older edifice. The faults typically lacked sediment cover, and in one case a very fresh, sediment-free fault trended along the base of a steep cliff. This suggested the faults were much younger than the 1720 eruption, an observation in accord with intense seismicity recorded in this area. The faults provided exposures of older rocks, which included abundant breccia and lesser clearly identified pillows or thick lava flows. The NW quadrant contains two small, shallow, elliptical craters. These lie side-by-side and crosscut inferred 1720s-age tuffs. One crater held a lava lake, the body of which apparently withdrew or subsided

  8. A Viable Microbial Community in a Subglacial Volcanic Crater Lake, Iceland

    NASA Astrophysics Data System (ADS)

    Gaidos, Eric; Lanoil, Brian; Thorsteinsson, Thorsteinn; Graham, Andrew; Skidmore, Mark; Han, Suk-Kyun; Rust, Terri; Popp, Brian

    2004-09-01

    We describe a viable microbial community in a subglacial lake within the Grímsvötn volcanic caldera, Iceland. We used a hot water drill to penetrate the 300-m ice shelf and retrieved lake water and volcanic tephra sediments. We also acquired samples of borehole water before and after penetration to the lake, overlying glacial ice and snow, and water from a nearby subaerial geothermal lake for comparative analyses. Lake water is at the freezing point and fresh (total dissolved solids = 260 mg L-1). Detectable numbers of cells were found in samples of the lake water column and tephra sediments: 2 × 104 ml-1 and 4 × 107 g-1, respectively. Plate counts document abundant cold-adapted cultivable organisms in the lake water, but not in the borehole (before penetration) or glacial ice. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from genomic DNA extracted from Gr??msv??tn samples indicates that the lake community is distinct from the assemblages of organisms in borehole water (before penetration) and the overlying ice and snow. Sequencing of selected DGGE bands revealed that many sequences are highly similar to known psychrophilic organisms or cloned DNA from other cold environments. Significant uptake of 14C-labeled bicarbonate occurred in dark, low-temperature incubations of lake water samples, indicating the presence of autotrophs. Acetylene reduction assays under similar incubation conditions showed no significant nitrogen fixation potential by lake water samples. This may be a consequence of the inhibition of diazotrophy by nitrogen in the lake.

  9. Isotope hydrology of El Chichón volcano-hydrothermal system; a coupled system of crater lake and hot springs

    NASA Astrophysics Data System (ADS)

    Peiffer, L.; Taran, Y.; Rouwet, D.

    2010-12-01

    The catastrophic 1982 eruption of El Chichón (>1.5 km3 of erupted material) opened the upper hundred meters of the existing volcano-hydrothermal system. In the new formed 200m-deep crater a large shallow crater lake and numerous hot springs were formed. The lake existence and its salinity depend on the precipitation (~4000 mm/y) as well as a group of geyser-like neutral saline springs (source of Cl and SO4) and hydrothermal steam vents discharging into the lake (source of SO4). The chemistry of these “Soap Pool” (SP) springs evolved from >13,000 ppm of Cl in 1995 to ~2000-3000 ppm of Cl in 2006. Since 2006, this Cl-concentration in SP waters is constant. Similar concentrations of Cl are observed in most flank hot springs located at altitudes of ~ 600 m asl, 2-3 km from the crater. Therefore, it can be suggested that the flank springs, crater lake and crater hot springs are manifestations of the upper, relatively shallow volcano-hydrothermal system developed beneath the crater in the volcano edifice. Water isotopic composition of all types of thermal and fresh waters including fumarolic steam condensates (>100 samples collected in 1995-2010) allow to classify and distinguish different processes of shallow mixing, boiling, evaporation and water-rock isotope exchange. All spring waters from the upper system have meteoric origin, with the isotopic composition plotting close to the meteoric water line. Crater waters are strongly evolved due to shallow boiling and loss of steam. Isotopic composition of water from the lower, deep hydrothermal system is characterized by a significant positive oxygen isotopic shift and a strong Cl-d18O linear correlation. Waters from numerous cold springs that drain pyroclastic deposits demonstrate a clear negative oxygen shift. Some problems related to water isotopic composition are still remain unresolved: (1) we cannot find any traces of the infiltrated isotopically heavy lake waters, i.e., the seepage from the lake at the volcano

  10. Spatial characterization of acid rain stress in Canadian Shield lakes

    NASA Technical Reports Server (NTRS)

    Tanis, Fred J.

    1986-01-01

    A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forests. The number of lakes affected in northeastern United States and on the Canadian Shield is thought to be enormous. Seasonal changes in lake transparency are examined relative to annual acidic load. The relationship between variations in lake acidification and ecophysical units is being examined. Finally, the utility of Thematic Mapper (TM) based observations is being used to measure seasonal changes in the optical transparency in acid lakes.

  11. Crater Lakes on Mars: Development of Quantitative Thermal and Geomorphic Models

    NASA Technical Reports Server (NTRS)

    Barnhart, C. J.; Tulaczyk, S.; Asphaug, E.; Kraal, E. R.; Moore, J.

    2005-01-01

    Impact craters on Mars have served as catchments for channel-eroding surface fluids, and hundreds of examples of candidate paleolakes are documented [1,2] (see Figure 1). Because these features show similarity to terrestrial shorelines, wave action has been hypothesized as the geomorphic agent responsible for the generation of these features [3]. Recent efforts have examined the potential for shoreline formation by wind-driven waves, in order to turn an important but controversial idea into a quantitative, falsifiable hypothesis. These studies have concluded that significant wave-action shorelines are unlikely to have formed commonly within craters on Mars, barring Earth-like weather for approx.1000 years [4,5,6].

  12. Egg fatty acid composition from lake trout fed two Lake Michigan prey fish species.

    USGS Publications Warehouse

    Honeyfield, D.C.; Fitzsimons, J.D.; Tillitt, D.E.; Brown, S.B.

    2009-01-01

    We previously demonstrated that there were significant differences in the egg thiamine content in lake trout Salvelinus namaycush fed two Lake Michigan prey fish (alewife Alosa pseudoharengus and bloater Coregonus hoyi). Lake trout fed alewives produced eggs low in thiamine, but it was unknown whether the consumption of alewives affected other nutritionally important components. In this study we investigated the fatty acid composition of lake trout eggs when females were fed diets that resulted in different egg thiamine concentrations. For 2 years, adult lake trout were fed diets consisting of four combinations of captured alewives and bloaters (100% alewives; 65% alewives, 35% bloaters; 35% alewives, 65% bloaters; and 100% bloaters). The alewife fatty acid profile had higher concentrations of arachidonic acid and total omega-6 fatty acids than the bloater profile. The concentrations of four fatty acids (cis-13, 16-docosadienoic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) were higher in bloaters than in alewives. Although six fatty acid components were higher in lake trout eggs in 2001 than in 2000 and eight fatty acids were lower, diet had no effect on any fatty acid concentration measured in lake trout eggs in this study. Based on these results, it appears that egg fatty acid concentrations differ between years but that the egg fatty acid profile does not reflect the alewife-bloater mix in the diet of adults. The essential fatty acid content of lake trout eggs from females fed alewives and bloaters appears to be physiologically regulated and adequate to meet the requirements of developing embryos.

  13. Geochemical monitoring of Chichón volcano (México) trough sulfur speciation of the crater lake's water

    NASA Astrophysics Data System (ADS)

    Casas, Ana Silvia; Aurora Armienta, Maria; Guadalupe Ramos, Silvia

    2015-04-01

    Monitoring of El Chichón volcanic activity is a very important given its eruption of March 28th, 1982 that was the worst volcanic disaster of the modern era in Mexico. To help mitigation of volcanic risk, we intend the establishment of an analytical methodology for the determining various sulfur species (S2-, SO3 2-, S4O6 2-, SO4 2-) occurring in the crater lake which was formed after the 1982 eruption. These species were determined through HPL Chromatography with the aim of establishing links between their presence and concentrations, the general physical and chemical characteristics of the lake, seasonal variations and the activity of El Chichón volcano. Besides, knowledge of sulfur species behavior will contribute to have a better knowledge of the state the hydrothermal system, and the internal dynamics of the volcano, and provide more information to determine periods of increasing hazard. This paper presents advances in the development of the methodologies for the analysis of the above mentioned sulfur species. We have identified the analytical procedures for sampling and analysis of these species (preservation, operating conditions of the equipment, number of samples, dilution, etc.) according to various studies in different volcanoes with crater lakes (Volcano Poas, Costa Rica; Kusatsu-Shirane, Japan). Water samples collected at various locations of the lake on March 29th, and July 11th and October 3rd, 2014, have been analyzed for major ions and sulfur species. Results are being related to the volcanic behavior. Results obtained: Average concentrations (mg/L) at one sampling site: • Sulphide: 1.75 in March, 1.82 in July and 4.99 in October • Sulphite: 4.16 in March, 1.89 in July and 25.23 in October • Tetrathionate: 236.88 in March, 247.46 in July and 152.96 in October • Sulphate: 618.51 in March, 609.91 in July and 620.18 in October Preliminary conclusions: • The proposed Chromatographic method has been successful to separate these sulfur

  14. Investigating crater lake warming using ASTER thermal imagery: Case studies at Ruapehu, Poás, Kawah Ijen, and Copahué Volcanoes

    NASA Astrophysics Data System (ADS)

    Trunk, Laura; Bernard, Alain

    2008-12-01

    A two-channel or split-window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Lake Yugama on Kusatsu-Shirane volcano in Japan in order to measure the temperature of its crater lake. These temperature calculations were validated using lake water temperatures that were collected on the ground. Overall, the agreement between the temperatures calculated using the split-window method and ground truth is quite good, typically ± 1.5 °C for cloud-free images. Data from fieldwork undertaken in the summer of 2004 at Kusatsu-Shirane allow a comparison of ground-truth data with the radiant temperatures measured using ASTER imagery. Further images were analyzed of Ruapehu, Poás, Kawah Ijen, and Copahué volcanoes to acquire time-series of lake temperatures. A total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed. Results of the split-window algorithm applied to ASTER images are reliable for monitoring thermal changes in active volcanic lakes. These temperature data, when considered in conjunction with traditional volcano monitoring techniques, lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting.

  15. Spatial characterization of acid rain stress in Canadian Shield Lakes

    NASA Technical Reports Server (NTRS)

    Tanis, F. J.; Marshall, E. M.

    1989-01-01

    The lake acidification in Northern Ontario was investigated using LANDSAT TM to sense lake volume reflectance and also to provide important vegetation and terrain characteristics. The purpose of this project was to determine the ability of LANDSAT to assess water quality characteristics associated with lake acidification. Results demonstrate that a remote sensor can discriminate lake clarity based upon reflection. The basic hypothesis is that seasonal and multi-year changes in lake optical transparency are indicative of sensitivity to acidic deposition. In many acid-sensitive lakes optical transparency is controlled by the amount of dissolved organic carbon present. Seasonal changes in the optical transparency of lakes can potentially provide an indication of the stress due to acid deposition and loading.

  16. Hydrogeologic controls on the groundwater interactions with an acidic lake in karst terrain, Lake Barco, Florida

    USGS Publications Warehouse

    Lee, T.M.

    1996-01-01

    Transient groundwater interactions and lake stage were simulated for Lake Barco, an acidic seepage lake in the mantled karst of north central Florida. Karst subsidence features affected groundwater flow patterns in the basin and groundwater fluxes to and from the lake. Subsidence features peripheral to the lake intercepted potential groundwater inflow and increased leakage from the shallow perimeter of the lake bed. Simulated groundwater fluxes were checked against net groundwater flow derived from a detailed lake hydrologic budget with short-term lake evaporation computed by the energy budget method. Discrepancies between modeled and budget- derived net groundwater flows indicated that the model underestimated groundwater inflow, possibly contributed to by transient water table mounding near the lake. Recharge from rainfall reduced lake leakage by 10 to 15 times more than it increased groundwater inflow. As a result of the karst setting, the contributing groundwater basin to the lake was 2.4 ha for simulated average rainfall conditions, compared to the topographically derived drainage basin area of 81 ha. Short groundwater inflow path lines and rapid travel times limit the contribution of acid-neutralizing solutes from the basin, making Lake Barco susceptible to increased acidification by acid rain.

  17. Is acid rain impacting the Sudetic lakes?

    PubMed

    Sienkiewicz, Elwira; Gasiorowski, Michał; Hercman, Helena

    2006-10-01

    The diatoms and Cladocera (Crustacea) remains from two lakes in the Sudets Mountains were analyzed to indicate an influence of acidification induced by anthropogenic factors during the last 150 years. The border area of the Czech Republic, Germany and Poland, the so-called "Black Triangle", has been strongly impacted by developed industry for several decades. The most visible effect of this process is the destruction of mountain forests in the region by acid rains. The diatom communities of Mały Staw and Wielki Staw show that acid rain has strongly affected water biota. Diatom-inferred pH reconstruction suggests major acidification during the last two decades. This process was controlled mainly by anthropogenic factors. Cladoceran records also presented changes of dominant taxa in this period and point to significant changes in living conditions. The discovery of a pH decrease during the last decade is contradictory to emissions data that suggest decrease in industrial pollution.

  18. Acidic lakes and streams in the United States: The role of acidic deposition

    SciTech Connect

    Baker, L.A.; Herlihy, A.T.; Kaufmann, P.R.; Eilers, J.M.

    1991-01-01

    A statistically designed survey of lakes and streams in acid-sensitive areas of the United States, the National Surface Water Survey (NSWS), was used to identify the role of acidic deposition, relative to other factors, in causing acidic conditions in 1,181 lakes and 4,668 streams. Atmospheric deposition is the dominant source of acid anions in 75% of the acidic lakes and 47% of the acidic streams. Organic anions are dominant in one-fourth of the acidic lakes and streams; acidic mine drainage is the dominant acid source in 25% of the acidic streams. Other causes of acidic conditions are relatively unimportant on a regional scale. Nearly all the deposition-dominated acidic systems were found in six well-delineated subpopulations that represent about one-fourth of the NSWS lake population and one-third of the NSWS stream population.

  19. Palos Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Palos Crater has been suggested as a future landing site for Mars Missions. This crater has a channel called Tinto Vallis, which enters from the south. This site was suggested as a landing site because it may contain lake deposits. Palos Crater is named in honor of the port city in Spain from which Christopher Columbus sailed on his way to the New World in August of 1492. The floor of Palos Crater appears to be layered in places providing further evidence that this site may in fact have been the location of an ancient lake.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. Whole-genome sequencing reveals small genomic regions of introgression in an introduced crater lake population of threespine stickleback.

    PubMed

    Yoshida, Kohta; Miyagi, Ryutaro; Mori, Seiichi; Takahashi, Aya; Makino, Takashi; Toyoda, Atsushi; Fujiyama, Asao; Kitano, Jun

    2016-04-01

    Invasive species pose a major threat to biological diversity. Although introduced populations often experience population bottlenecks, some invasive species are thought to be originated from hybridization between multiple populations or species, which can contribute to the maintenance of high genetic diversity. Recent advances in genome sequencing enable us to trace the evolutionary history of invasive species even at whole-genome level and may help to identify the history of past hybridization that may be overlooked by traditional marker-based analysis. Here, we conducted whole-genome sequencing of eight threespine stickleback (Gasterosteus aculeatus) individuals, four from a recently introduced crater lake population and four of the putative source population. We found that both populations have several small genomic regions with high genetic diversity, which resulted from introgression from a closely related species (Gasterosteus nipponicus). The sizes of the regions were too small to be detected with traditional marker-based analysis or even some reduced-representation sequencing methods. Further amplicon sequencing revealed linkage disequilibrium around an introgression site, which suggests the possibility of selective sweep at the introgression site. Thus, interspecies introgression might predate introduction and increase genetic variation in the source population. Whole-genome sequencing of even a small number of individuals can therefore provide higher resolution inference of history of introduced populations. PMID:27069575

  1. Whole-genome sequencing reveals small genomic regions of introgression in an introduced crater lake population of threespine stickleback.

    PubMed

    Yoshida, Kohta; Miyagi, Ryutaro; Mori, Seiichi; Takahashi, Aya; Makino, Takashi; Toyoda, Atsushi; Fujiyama, Asao; Kitano, Jun

    2016-04-01

    Invasive species pose a major threat to biological diversity. Although introduced populations often experience population bottlenecks, some invasive species are thought to be originated from hybridization between multiple populations or species, which can contribute to the maintenance of high genetic diversity. Recent advances in genome sequencing enable us to trace the evolutionary history of invasive species even at whole-genome level and may help to identify the history of past hybridization that may be overlooked by traditional marker-based analysis. Here, we conducted whole-genome sequencing of eight threespine stickleback (Gasterosteus aculeatus) individuals, four from a recently introduced crater lake population and four of the putative source population. We found that both populations have several small genomic regions with high genetic diversity, which resulted from introgression from a closely related species (Gasterosteus nipponicus). The sizes of the regions were too small to be detected with traditional marker-based analysis or even some reduced-representation sequencing methods. Further amplicon sequencing revealed linkage disequilibrium around an introgression site, which suggests the possibility of selective sweep at the introgression site. Thus, interspecies introgression might predate introduction and increase genetic variation in the source population. Whole-genome sequencing of even a small number of individuals can therefore provide higher resolution inference of history of introduced populations.

  2. Bacterioplankton communities of Crater Lake, OR: Dynamic changes with euphotic zone food web structure and stable deep water populations

    USGS Publications Warehouse

    Urbach, E.; Vergin, K.L.; Larson, G.L.; Giovannoni, S.J.

    2007-01-01

    The distribution of bacterial and archaeal species in Crater Lake plankton varies dramatically over depth and with time, as assessed by hybridization of group-specific oligonucleotides to RNA extracted from lakewater. Nonmetric, multidimensional scaling (MDS) analysis of relative bacterial phylotype densities revealed complex relationships among assemblages sampled from depth profiles in July, August and September of 1997 through 1999. CL500-11 green nonsulfur bacteria (Phylum Chloroflexi) and marine Group I crenarchaeota are consistently dominant groups in the oxygenated deep waters at 300 and 500 m. Other phylotypes found in the deep waters are similar to surface and mid-depth populations and vary with time. Euphotic zone assemblages are dominated either by ??-proteobacteria or CL120-10 verrucomicrobia, and ACK4 actinomycetes. MDS analyses of euphotic zone populations in relation to environmental variables and phytoplankton and zooplankton population structures reveal apparent links between Daphnia pulicaria zooplankton population densities and microbial community structure. These patterns may reflect food web interactions that link kokanee salmon population densities to community structure of the bacterioplankton, via fish predation on Daphnia with cascading consequences to Daphnia bacterivory and predation on bacterivorous protists. These results demonstrate a stable bottom-water microbial community. They also extend previous observations of food web-driven changes in euphotic zone bacterioplankton community structure to an oligotrophic setting. ?? 2007 Springer Science+Business Media B.V.

  3. Acid rain stimulation of Lake Michigan phytoplankton growth

    USGS Publications Warehouse

    Manny, Bruce A.; Fahnenstiel, G.L.; Gardner, W.S.

    1987-01-01

    Three laboratory experiments demonstrated that additions of rainwater to epilimnetic lake water collected in southeastern Lake Michigan stimulated chlorophyll a production more than did additions of reagent-grade water during incubations of 12 to 20 d. Chlorophyll a production did not begin until 3–5 d after the rain and lake water were mixed. The stimulation caused by additions of rain acidified to pH 3.0 was greater than that caused by additions of untreated rain (pH 4.0–4.5). Our results support the following hypotheses: (1) Acid rain stimulates the growth of phytoplankton in lake water; (2) phosphorus in rain appears to be the factor causing this stimulation. We conclude that acid rain may accelerate the growth of epilimnetic phytoplankton in Lake Michigan (and other similar lakes) during stratification when other sources of bioavailable phosphorus to the epilimnion are limited

  4. Cementation and Aqueous Alteration of a Sandstone Unit Under Acidic Conditions in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Yen, A. S.; Blake, D. F.; Ming, D. W.; Morris, R. V.; Gellert, R.; Clark, B.; Vaniman, D. T.; Chipera, S. J.; Thompson, L. M.; Bristow, T. F.; Rampe, E. B.; Crisp, J. A.

    2016-01-01

    The Curiosity rover landed on Mars in August 2012 to explore the sedimentary history and to assess the habitability of Gale Crater. After 1200 sols of surface operations and over 12 km of traverse distance, the mineralogy of 10 samples has been determined by the CheMin X-ray diffractometer (XRD) and the chemical composition of nearly 300 targets has been established by the Alpha Particle X-ray Spectrometer (APXS). Light-toned fracture zones containing elevated concentrations of silica have been studied by Curiosity's instruments to determine the nature of the fluids that resulted in the enrichment of SiO2. Multiple fluid exposures are evident, and the chemistry and mineralogy data indicate at least two aqueous episodes may have occurred under acidic conditions.

  5. Temporal bacterial diversity and detection of putative methanotrophs in surface mats of Lonar crater lake.

    PubMed

    Surakasi, Venkata Prasad; Antony, Chakkiath Paul; Sharma, Sashikant; Patole, Milind S; Shouche, Yogesh S

    2010-10-01

    The phylogenetic diversity of bacterial communities in microbial mats of two different seasons from saline and hyperalkaline Lonar Lake was investigated using 16S rRNA gene library analysis. Arthrospira (Cyanobacteria) related clones (>80% of total clones) dominated libraries of both the seasons. Clear differences were found in both the seasons as the operational taxonomic units (OTUs) related to Fusibacter (LAI-1 and LAI-59) and Tindallia magadiensis (LAI-27) found in post-monsoon were not found in the pre-monsoon library. Likewise, OTUs related to Planococcus rifietensis (LAII-67), Bordetella hinzii (LAII-2) and Methylobacterium variabile (LAII-25) found in the pre-monsoon were not found in post-monsoon. The study was extended to identify methanotrophs in the surface mats. Libraries constructed with type I and type II methanotroph specific 16S rRNA gene primers showed the presence of clones (LAMI-99 and LAMII-2) closely related to Methylomicrobium buryaticum and Beijerinckiaceae family members. Denaturing gradient gel electrophoresis (DGGE) fingerprinting based on protein-coding genes (pmoA and mxaF) further confirmed the detection of Methylomicrobium sp. Hence, we report here for the first time the detection of putative methanotrophs in surface mats of Lonar Lake. The finding of clones related to organisms with interesting functional attributes such as assimilation of C(1) compounds (LAII-25, LAMI-39, LAMI-99 and LAMII-2), non-sulfur photosynthetic bacteria (LAMII-43) and clones distantly affiliated to organisms of heavily polluted environments (LAI-59 and LAMII-52), is of significant note. These preliminary results would direct future studies on the functional dynamics of microbial mat associated food web chain in the extreme environment. PMID:20586073

  6. Temporal bacterial diversity and detection of putative methanotrophs in surface mats of Lonar crater lake.

    PubMed

    Surakasi, Venkata Prasad; Antony, Chakkiath Paul; Sharma, Sashikant; Patole, Milind S; Shouche, Yogesh S

    2010-10-01

    The phylogenetic diversity of bacterial communities in microbial mats of two different seasons from saline and hyperalkaline Lonar Lake was investigated using 16S rRNA gene library analysis. Arthrospira (Cyanobacteria) related clones (>80% of total clones) dominated libraries of both the seasons. Clear differences were found in both the seasons as the operational taxonomic units (OTUs) related to Fusibacter (LAI-1 and LAI-59) and Tindallia magadiensis (LAI-27) found in post-monsoon were not found in the pre-monsoon library. Likewise, OTUs related to Planococcus rifietensis (LAII-67), Bordetella hinzii (LAII-2) and Methylobacterium variabile (LAII-25) found in the pre-monsoon were not found in post-monsoon. The study was extended to identify methanotrophs in the surface mats. Libraries constructed with type I and type II methanotroph specific 16S rRNA gene primers showed the presence of clones (LAMI-99 and LAMII-2) closely related to Methylomicrobium buryaticum and Beijerinckiaceae family members. Denaturing gradient gel electrophoresis (DGGE) fingerprinting based on protein-coding genes (pmoA and mxaF) further confirmed the detection of Methylomicrobium sp. Hence, we report here for the first time the detection of putative methanotrophs in surface mats of Lonar Lake. The finding of clones related to organisms with interesting functional attributes such as assimilation of C(1) compounds (LAII-25, LAMI-39, LAMI-99 and LAMII-2), non-sulfur photosynthetic bacteria (LAMII-43) and clones distantly affiliated to organisms of heavily polluted environments (LAI-59 and LAMII-52), is of significant note. These preliminary results would direct future studies on the functional dynamics of microbial mat associated food web chain in the extreme environment.

  7. Uranium and minor-element partitioning in Fe-Ti oxides and zircon from partially melted granodiorite, Crater Lake, Oregon

    SciTech Connect

    La Tourrette, T.Z.; Burnett, D.S. ); Bacon C.R. )

    1991-02-01

    Crystal-liquid partitioning in Fe-Ti oxides and zircon was studied in partially melted granodiorite blocks ejected during the climactic eruption of Mt. Mazama (Crater Lake), Oregon. The blocks, which contain up to 33% rhyolite glass (75 wt% SiO{sub 2}), are interpreted to be portions of the magma chamber walls that were torn off during eruption. The glass is clear and well homogenized for all measured elements except Zr. Results for Fe-Ti oxides give D{sub U}{sup oxide/liq} {approx} 0.1. Partitioning of Mg, Mn, Al, Si, V, and Cr in Fe-Ti oxides indicates that grains surrounded by glass are modestly well equilibrated with the melt for many of the minor elements, while those that are inclusions in relict plagioclase are not. Uranium and ytterbium inhomogeneities in zircons indicate that the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons faster that the zircons were dissolving. Based on the authors measurements and given their low abundances in most rocks, Fe-Ti oxides probably do not play a major role in U-Th fractional during partial melting. The partial melts were undersaturated with zircon and apatite, but both phases are present in the authors samples. This demonstrates an actual case of nonequilibrium source retention of accessory phases, which in general could be an important trace element fractionation mechanism. Their results do not support the hypothesis that liquid structure is the dominant factor controlling trace-element partitioning in high-silica rhyolites.

  8. Uranium and minor-element partitioning in Fe-Ti oxides and zircon from partially melted granodiorite, Crater Lake, Oregon

    USGS Publications Warehouse

    Tourrette, T.Z.L.; Burnett, D.S.; Bacon, C.R.

    1991-01-01

    Crystal-liquid partitioning in Fe-Ti oxides and zircon was studied in partially melted granodiorite blocks ejected during the climactic eruption of Mt. Mazama (Crater Lake), Oregon. The blocks, which contain up to 33% rhyolite glass (75 wt% SiO2), are interpreted to be portions of the magma chamber walls that were torn off during eruption. The glass is clear and well homogenized for all measured elements except Zr. Results for Fe-Ti oxides give DUoxide/liq ??? 0.1. Partitioning of Mg, Mn, Al, Si, V, and Cr in Fe-Ti oxides indicates that grains surrounded by glass are moderately well equilibrated with the melt for many of the minor elements, while those that are inclusions in relict plagioclase are not. Uranium and ytterbium inhomogeneities in zircons indicate that the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons faster than the zircons were dissolving. Minimum U, Y, and P concentrations in zircons give maximum DUzrc/liq = 13,DYzrc/liq = 23, and DPzrc/liq = 1, but these are considerably lower than reported by other workers for U and Y. Based on our measurements and given their low abundances in most rocks, Fe-Ti oxides probably do not play a major role in U-Th fractionation during partial melting. The partial melts were undersaturated with zircon and apatite, but both phases are present in our samples. This demonstrates an actual case of non-equilibrium source retention of accessory phases, which in general could be an important trace-element fractionation mechanism. Our results do not support the hypothesis that liquid structure is the dominant factor controlling trace-element partitioning in high-silica rhyolites. Rough calculations based on Zr gradients in the glass indicate that the samples could have been partially molten for 800 to 8000 years. ?? 1991.

  9. Microbial ecology of acid strip mine lakes in southern Indiana

    SciTech Connect

    Gyure, R.A.

    1986-01-01

    In this study, the author examined the limnology and microbial ecology of two acid strip mine lakes in the Greene-Sullivan State Forest near Dugger, Indiana. Reservoir 29 is a larger lake (225 ha) with water column pH of 2.7 and sediment pH of 3.8. Lake B, a smaller (20 ha) lake to the south of Reservoir 29, also has an acidic water column (pH 3.4) but more neutral sediments (pH 6.2). Both have very high sulfate concentrations: 20-30 mM in the water column and as high as 100 mM in the hypolimnion of Lake B. Low allochthonous carbon and nutrient input characterize these lakes as oligotrophic, although algal biomass is higher than would be expected for this trophic status. In both lakes, algal populations are not diverse, with a few species of single-celled Chlorophyta and euglenoids dominating. Algal biomass is concentrated in a thin 10 cm layer at the hypolimnion/metalimnion interface, although light intensity at this depth is low and severely limits productivity. Bacterial activity based on /sup 14/C-glucose incorporation is highest in the hypolimnion of both lakes, and sulfate-reduction is a dominant process in the sediments. Rates of sulfate-reduction compare with those in other freshwater environments, but are not as high as rates measured in high sulfate systems like saltmarsh and marine sediments.

  10. High-resolution digital elevation dataset for Crater Lake National Park and vicinity, Oregon, based on LiDAR survey of August-September 2010 and bathymetric survey of July 2000

    USGS Publications Warehouse

    Robinson, Joel E.

    2012-01-01

    Crater Lake partially fills the caldera that formed approximately 7,700 years ago during the eruption of a 12,000-foot volcano known as Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama devastated the surrounding landscape, left a thick deposit of pumice and ash in adjacent valleys, and spread a blanket of volcanic ash as far away as southern Canada. Because the Crater Lake region is potentially volcanically active, knowledge of past events is important to understanding hazards from future eruptions. Similarly, because the area is seismically active, documenting and evaluating geologic faults is critical to assessing hazards from earthquakes. As part of the American Recovery and Reinvestment Act (ARRA) of 2009, the U.S. Geological Survey was awarded funding for high-precision airborne LiDAR (Light Detection And Ranging) data collection at several volcanoes in the Cascade Range through the Oregon LiDAR Consortium, administered by the Oregon Department of Geology and Mineral Industries (DOGAMI). The Oregon LiDAR Consortium contracted with Watershed Sciences, Inc., to conduct the data collection surveys. Collaborating agencies participating with the Oregon LiDAR Consortium for data collection in the Crater Lake region include Crater Lake National Park (National Park Service) and the Federal Highway Administration. In the immediate vicinity of Crater Lake National Park, 798 square kilometers of LiDAR data were collected, providing a digital elevation dataset of the ground surface beneath forest cover with an average resolution of 1.6 laser returns/m2 and both vertical and horizontal accuracies of ±5 cm. The LiDAR data were mosaicked in this report with bathymetry of the lake floor of Crater Lake, collected in 2000 using high-resolution multibeam sonar in a collaborative effort between the U.S. Geological Survey, Crater Lake National Park, and the Center for Coastal and Ocean Mapping at the University of New Hampshire. The bathymetric survey

  11. Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Rampe, E. B.; Ming, D. W.; Vaniman, D. T.; Blake, D. F.; Chipera, S.; Morris, R. V.; Bish, D. L.; Cavanagh, P.; Achilles, C.; Bristow, T.; Fairen, A.; Morrison, S. M.; Treiman, A. H.; Crisp, J. A.; Downs, R. T.; Farmer, J. D.; Fendrich, K.; Morookian, J.

    2015-12-01

    The Pahrump Hills region of Gale crater is a ~12 m thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF. Results from CheMin show that these samples have variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, cristobalite, and X-ray amorphous material. The presence of jarosite in all samples indicates these rocks were affected by acid-sulfate alteration, and the mineralogical and geochemical trends observed through the section may give more insight into this process. Geochemical data measured by APXS show enrichment in Si and depletion in Mg moving up section. CheMin data show that cristobalite is more abundant up section, whereas pyroxene and phyllosilicates are more abundant at the bottom of the section. Based on mineralogical and geochemical trends and diagenetic features observed in the Pahrump Hills, we hypothesize that the sediments were altered in-situ by acid-sulfate fluids moving down from the top of the section to leach mobile elements, dissolve the minerals most susceptible to acidic alteration, and precipitate secondary silica at the top of the section. Alternative interpretations of the observed mineralogical and geochemical data are possible, including the hypothesis that the redox conditions of the body of water in which the sediments were deposited changed over time.

  12. Spatial characterization of acid rain stress in Canadian Shield Lakes

    NASA Technical Reports Server (NTRS)

    Tanis, Fred J.

    1987-01-01

    The acidification of lake waters from airborne pollution is of continental proportions both in North America and Europe. A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forest. The number of lakes affected in northeastern U.S. and on the Canadian Shield is though to be enormous. How seasonal changes in lake transparency are related to annual acidic load was examined. The relationship between variations in lake acidification and ecophysical units was also examined. The utility of Thematic Mapper based observations to measure seasonal changes in the optical transparency in acid lakes was investigated. The potential for this optical response is related to a number of local ecophysical factors with bedrock geology being, perhaps, the most important. Other factors include sulfate deposition, vegetative cover, and terrain drainage/relief. The area of southern Ontario contains a wide variety of geologies from the most acid rain sensitive granite quartzite types to the least sensitive limestone dolomite sediments. Annual sulfate deposition ranges from 1.0 to 4.0 grams/sq m.

  13. Extremely acid Permian lakes and ground waters in North America

    USGS Publications Warehouse

    Benison, K.C.; Goldstein, R.H.; Wopenka, B.; Burruss, R.C.; Pasteris, J.D.

    1998-01-01

    Evaporites hosted by red beds (red shales and sandstones), some 275-265 million years old, extend over a large area of the North American mid- continent. They were deposited in non-marine saline lakes, pans and mud- flats, settings that are typically assumed to have been alkaline. Here we use laser Raman microprobe analyses of fluid inclusions trapped in halites from these Permian deposits to argue for the existence of highly acidic (pH < 1) lakes and ground waters. These extremely acidic systems may have extended over an area of 200,000 km2. Modern analogues of such systems may be natural acid lake and groundwater systems (pH ~2-4) in southern Australia. Both the ancient and modern acid systems are characterized by closed drainage, arid climate, low acid-neutralizing capacity, and the oxidation of minerals such as pyrite to generate acidity. The discovery of widespread ancient acid lake and groundwater systems demands a re-evaluation of reconstructions of surface conditions of the past, and further investigations of the geochemistry and ecology of acid systems in general.

  14. Detecting acid precipitation impacts on lake water quality

    NASA Astrophysics Data System (ADS)

    Loftis, Jim C.; Taylor, Charles H.

    1989-09-01

    The United States Environmental Protection Agency is planning to expand its long-term monitoring of lakes that are sensitive to acid deposition effects. Effective use of resources will require a careful definition of the statistical objectives of monitoring, a network design which balances spatial and temporal coverage, and a sound approach to data analysis. This study examines the monitoring objective of detecting trends in water quality for individual lakes and small groups of lakes. Appropriate methods of trend analysis are suggested, and the power of trend detection under seasonal (quarterly) sampling is compared to that of annual sampling. The effects of both temporal and spatial correlation on trend detection ability are described.

  15. Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation.

    PubMed

    Martin, Christopher H; Cutler, Joseph S; Friel, John P; Dening Touokong, Cyrille; Coop, Graham; Wainwright, Peter C

    2015-06-01

    One of the most celebrated examples of sympatric speciation in nature are monophyletic radiations of cichlid fishes endemic to Cameroon crater lakes. However, phylogenetic inference of monophyly may not detect complex colonization histories involving some allopatric isolation, such as double invasions obscured by genome-wide gene flow. Population genomic approaches are better suited to test hypotheses of sympatric speciation in these cases. Here, we use comprehensive sampling from all four sympatric crater lake cichlid radiations in Cameroon and outgroups across Africa combined with next-generation sequencing to genotype tens of thousands of SNPs. We find considerable evidence of gene flow between all four radiations and neighboring riverine populations after initial colonization. In a few cases, some sympatric species are more closely related to outgroups than others, consistent with secondary gene flow facilitating their speciation. Our results do not rule out sympatric speciation in Cameroon cichlids, but rather reveal a complex history of speciation with gene flow, including allopatric and sympatric phases, resulting in both reproductively isolated species and incipient species complexes. The best remaining non-cichlid examples of sympatric speciation all involve assortative mating within microhabitats. We speculate that this feature may be necessary to complete the process of sympatric speciation in nature.

  16. Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation.

    PubMed

    Martin, Christopher H; Cutler, Joseph S; Friel, John P; Dening Touokong, Cyrille; Coop, Graham; Wainwright, Peter C

    2015-06-01

    One of the most celebrated examples of sympatric speciation in nature are monophyletic radiations of cichlid fishes endemic to Cameroon crater lakes. However, phylogenetic inference of monophyly may not detect complex colonization histories involving some allopatric isolation, such as double invasions obscured by genome-wide gene flow. Population genomic approaches are better suited to test hypotheses of sympatric speciation in these cases. Here, we use comprehensive sampling from all four sympatric crater lake cichlid radiations in Cameroon and outgroups across Africa combined with next-generation sequencing to genotype tens of thousands of SNPs. We find considerable evidence of gene flow between all four radiations and neighboring riverine populations after initial colonization. In a few cases, some sympatric species are more closely related to outgroups than others, consistent with secondary gene flow facilitating their speciation. Our results do not rule out sympatric speciation in Cameroon cichlids, but rather reveal a complex history of speciation with gene flow, including allopatric and sympatric phases, resulting in both reproductively isolated species and incipient species complexes. The best remaining non-cichlid examples of sympatric speciation all involve assortative mating within microhabitats. We speculate that this feature may be necessary to complete the process of sympatric speciation in nature. PMID:25929355

  17. Direct evidence for the origin of low-18O silicic magmas: quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Adami, L.H.; Lanphere, M.A.

    1989-01-01

    Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower ??18O values (-3.4 to +4.9???) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0???). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T ??? 900??C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ??? 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have ??18O values ??? 0.5??? or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18O depletion in large, shallow silicic magma bodies. ?? 1989.

  18. Facies associations of rain-generated versus crater lake-withdrawal lahar deposits from Quaternary volcanoes, central Italy

    NASA Astrophysics Data System (ADS)

    Giordano, G.; De Rita, D.; Fabbri, M.; Rodani, S.

    2002-11-01

    volcano, grades laterally into a single, far-reaching, thick lahar deposit. The lahar deposit coarsens upward from coarse-ash, hyperconcentrated-flow deposit into a lithic-block-rich, debris-flow deposit. This lahar deposit has been interpreted to be directly derived from a pyroclastic flow and particularly related to the entrance of the pyroclastic flow into a pre-existing maar crater lake along the pyroclastic-flow path. The basal sand-size, hyperconcentrated-flow deposit is interpreted to represent early deposition from the fast frontal flood wave, whereas the coarse lithic-rich debris-flow deposit at the top may represent the rear of the lahar. The separation of the two facies can be related to processes of 'hydraulic sieving' operated by the lake water, which couples with ash particles, leaving behind the coarser fraction.

  19. Variability of passive gas emissions, seismicity, and deformation during crater lake growth at White Island Volcano, New Zealand, 2002-2006

    USGS Publications Warehouse

    Werner, C.; Hurst, T.; Scott, B.; Sherburn, S.; Christenson, B.W.; Britten, K.; Cole-Baker, J.; Mullan, B.

    2008-01-01

    We report on 4 years of airborne measurements of CO2, SO2, and H2S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbig processes to be investigated. CO2 emissions varied from a baseline of 250 to >2000 t d-1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level. The annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs, temporarily causing fractures to reduce in size in the upper conduit. SO2 emissions varied from 0 to >400 t d-1 and were clearly affected by scrubbing processes within the first year of take development. Scrubbing caused increases of SO42- and Cl- in lake waters, and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year. Careful measurements of the lake level and chemistry allowed estimates of the rate of H2O(g) and HCl(g) input into the lake and suggested that the molar abundances of major gas species (H2O, CO2, SO2, and HCl) during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods. The volume of magma estimated from CO2 emissions (0.0 15-0.04 km3) was validated by Cl- increases in the lake, suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region. The absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths. Two models of convection configurations are discussed. Copyright 2008 by the American Geophysical Union.

  20. Similar bacterial community composition in acidic mining lakes with different pH and lake chemistry.

    PubMed

    Kampe, Heike; Dziallas, Claudia; Grossart, Hans-Peter; Kamjunke, Norbert

    2010-10-01

    As extreme environmental conditions strongly affect bacterial community composition (BCC), we examined whether differences in pH-even at low pH-and in iron and sulfate concentrations lead to changes in BCC of acidic mining lakes. Thereby, we tested the following hypotheses: (1) diversity of the bacterial community in acidic lakes decreases with reducing pH, (2) BCC differs between epilimnion and hypolimnion, and (3) BCC in extremely acidic environments does not vary much over time. Therefore, we investigated the BCC of three acidic lakes with different pH values (2.3, 2.7, and 3.2) by denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of DGGE bands as well as catalyzed reporter deposition-FISH (CARD-FISH). BCC did not significantly vary among the studied lakes nor differ much between water layers. In contrast, BCC significantly changed over time, which is contradictory to our hypotheses. Bacterial communities were dominated by Alpha-, Beta-, and Gammaproteobacteria, whereas Actino- and Acidobacteria rarely occurred. Cell numbers of both free and attached bacteria were positively related to DOC concentration. Overall, low pH and extreme chemical conditions of the studied lakes led to similar assemblages of bacteria with pronounced temporal differences. This notion indicates that temporal changes in environmental conditions including food web structure also affect unique communities of bacteria thriving at low pH.

  1. Phosphate Stability in Diagenetic Fluids Constrains the Acidic Alteration Model for Lower Mt. Sharp Sedimentary Rocks in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Berger, J. A.; Schmidt, M. E.; Izawa, M. R. M.; Gellert, R.; Ming, D. W.; Rampe, E. B.; VanBommel, S. J.; McAdam, A. C.

    2016-01-01

    The Mars rover Curiosity has encountered silica-enriched bedrock (as strata and as veins and associated halos of alteration) in the largely basaltic Murray Fm. of Mt. Sharp in Gale Crater. Alpha Particle X-ray Spectrometer (APXS) investigations of the Murray Fm. revealed decreasing Mg, Ca, Mn, Fe, and Al, and higher S, as silica increased (Fig. 1). A positive correlation between SiO2 and TiO2 (up to 74.4 and 1.7 wt %, respectively) suggests that these two insoluble elements were retained while acidic fluids leached more soluble elements. Other evidence also supports a silica-retaining, acidic alteration model for the Murray Fm., including low trace element abundances consistent with leaching, and the presence of opaline silica and jarosite determined by CheMin. Phosphate stability is a key component of this model because PO4 3- is typically soluble in acidic water and is likely a mobile ion in diagenetic fluids (pH less than 5). However, the Murray rocks are not leached of P; they have variable P2O5 (Fig. 1) ranging from average Mars (0.9 wt%) up to the highest values in Gale Crater (2.5 wt%). Here we evaluate APXS measurements of Murray Fm. bedrock and veins with respect to phosphate stability in acidic fluids as a test of the acidic alteration model for the Lower Mt. Sharp rocks.

  2. Craters Filling Craters

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    In today's image the large crater retains its original bowl shaped interior and the radial surface pattern on the ejecta. Just to the south is a crater that has been infilled by ejecta from the larger crater. The overlapping of ejecta blankets can be used to get relative age relationships, in this case the smaller crater to the south formed first, and the larger crater formed sometime later.

    Image information: VIS instrument. Latitude 29.6, Longitude 96.3 East (263.7 West). 37 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. Sulfur Oxidation, Microbes And Acidity In A Mine Tailings Lake

    NASA Astrophysics Data System (ADS)

    Warren, L. A.; Bernier, L.

    2003-12-01

    Disposal of tailings (waste rock) aqueously is a common approach at mine sites to minimize oxidation of the associated sulfur minerals (pyrrhotite, pyrite) and the associated generation of acidity that accompanies this process. The study site, Moose Lake, receives tailings runoff at a nickel mine in Northern Ontario, which has rendered the lake highly acidic (surface pH values less than 3.5) with high metal loads and on-going acid export to off-site, downstream systems. To investigate the potential influence of microbial processes for acid generation, as well as characterizing any attendant influences for metal behaviour, the biogeochemistry of Moose Lake was characterized on a seasonal and a diel basis during the summer of 2002. Physico-chemical profiles were used to identify the area of strong redox gradient across the thermocline (typically 1 to 2 metres across this zone) on each sampling day. Samples at five depths within this redox gradient, were then collected for Fe3+/Fe2+, SO42-/H2S, metal and microbial samples, in addition to more highly resolved Hydrolab profiling. Samples were collected both during the lighted portion of the day (10am-12pm) and at dusk (6pm-8pm) to evaluate any contributions to S and Fe cycling attributed to photosynthetic activity. Results indicate a clear seasonal increase in acidity in the upper waters of the lake: pH values dropped from 3.19 in May to 2.90 in September. Further, a strong diel trend of increasing acidity (lower pH) from mid morning to dusk was also observed for each sampling period. Biotic control on S processes appears to be important associated with the thermocline region of the lake, whilst surficial processes occurring in the upper one to three meters are more consistent with a dominant abiotic control. Both pathways contribute to acidity generation, however the controls and rates differ. These results and implications for mitigation strategies will be presented.

  4. Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

    USGS Publications Warehouse

    Wright, Heather M.; Bacon, Charles R.; Vazquez, Jorge A.; Sisson, Thomas W.

    2012-01-01

    The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe–Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918–968 to ~950 to 845–895 °C). Oxygen fugacity began at nickel–nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite–rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3–4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and

  5. Thiamine and fatty acid content of Lake Michigan Chinook salmon

    USGS Publications Warehouse

    Honeyfield, D.C.; Peters, A.K.; Jones, M.L.

    2008-01-01

    Nutritional status of Lake Michigan Chinook salmon (Oncorhynchus tshawytscha) is inadequately documented. An investigation was conducted to determine muscle and liver thiamine content and whole body fatty acid composition in small, medium and large Chinook salmon. Muscle and liver thiamine concentrations were highest in small salmon, and tended to decrease with increasing fish size. Muscle thiamine was higher in fall than spring in large salmon. The high percentage of Chinook salmon (24-32% in fall and 58-71% in spring) with muscle thiamine concentration below 500 pmol/g, which has been associated with loss of equilibrium and death in other Great Lake salmonines, suggest that Chinook appear to rely less on thiamine than other Great Lakes species for which such low concentrations would be associated with thiamine deficiency (Brown et al. 2005b). A positive correlation was observed between liver total thiamine and percent liver lipids (r = 0.53, P < 0.0001, n = 119). In medium and large salmon, liver lipids were observed to be low in fish with less than 4,000 pmol/g liver total thiamine. In individuals with greater than 4,000 pmol/g liver thiamine, liver lipid increased with thiamine concentration. Individual fatty acids declined between fall and spring. Essential omega-3 fatty acids appear to be conserved as lipid content declined. Arachidonic acid (C20:4n6), an essential omega-6 fatty acid was not different between fall and spring, although the sum of omega-6 (Sw6) fatty acids declined over winter. Elevated concentrations of saturated fatty acids (sum) were observed in whole body tissue lipid. In summary, thiamine, a dietary essential vitamin, and individual fatty acids were found to vary in Lake Michigan Chinook salmon by fish size and season of the year.

  6. Methylophaga lonarensis sp. nov., a moderately haloalkaliphilic methylotroph isolated from the soda lake sediments of a meteorite impact crater.

    PubMed

    Antony, Chakkiath Paul; Doronina, Nina V; Boden, Rich; Trotsenko, Yuri A; Shouche, Yogesh S; Murrell, J Colin

    2012-07-01

    A moderately haloalkaliphilic methylotrophic bacterium possessing the ribulose monophosphate pathway for carbon assimilation, designated MPL(T), was isolated from Lonar Lake sediment microcosms that were oxidizing methane for two weeks. The isolate utilized methanol and was an aerobic, Gram-negative, asporogenous, motile, short rod that multiplied by binary fission. The isolate required NaHCO(3) or NaCl for growth and, although not auxotrophic for vitamin B(12), had enhanced growth with vitamin B(12). Optimal growth occurred with 0.5-2% (w/v) NaCl, at 28-30 °C and at pH 9.0-10.0. The cellular fatty acid profile consisted primarily of straight-chain saturated C(16:0) and unsaturated C(16:1)ω7c and C(18:1)ω7c. The major ubiquinone was Q-8. The dominant phospholipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Cells accumulated ectoine as the main compatible solute. The DNA G+C content was 50.0 mol%. The isolate exhibited 94.0-95.4% 16S rRNA gene sequence similarity with the type strains of methylotrophs belonging to the genus Methylophaga and 31% DNA-DNA relatedness with the reference strain, Methylophaga alcalica VKM B-2251(T). It is proposed that strain MPL(T) represents a novel species, Methylophaga lonarensis sp. nov. (type strain MPL(T)=VKM B-2684(T)=MCC 1002(T)).

  7. Morpho-Bathymetry of the Specchio di Venere Crater Lake, Pantelleria Island, Italy: Integration of GPS Surveys with non-GPS Data and Evidence of Sedimentary Control on Lake Bottom Topography

    NASA Astrophysics Data System (ADS)

    Madonia, P.; Cangemi, M.; Bellanca, A.; D'Alessandro, W.; Neri, R.; Failla, A.

    2009-12-01

    microbialites. Fig. 1 Specchio di Venere Crater Lake, Pantelleria Island, Italy

  8. Cratering mechanics

    NASA Technical Reports Server (NTRS)

    Ivanov, B. A.

    1986-01-01

    Main concepts and theoretical models which are used for studying the mechanics of cratering are discussed. Numerical two-dimensional calculations are made of explosions near a surface and high-speed impact. Models are given for the motion of a medium during cratering. Data from laboratory modeling are given. The effect of gravitational force and scales of cratering phenomena is analyzed.

  9. Lava Lake Level Drop and Related Ground Subsidence in the Nyiragongo Main Crater (D.R.Congo) Measured by Close-Range Photogrammetry and InSAR Time-Series

    NASA Astrophysics Data System (ADS)

    Smets, B.; d'Oreye, N.; Samsonov, S. V.; Nobile, A.; Geirsson, H.; Kervyn, F.

    2015-12-01

    Nyiragongo volcano is the most active African volcano and among the most active volcanoes on Earth. It is also among the infrequent volcanoes that host a long-lived lava lake. The morphology of the Nyiragongo main crater is characterized by 2 levels of remnant platforms partly preserved and attached to its inner flanks, which correspond to former lava lake levels, and by a bottom "active" platform, which delimits the current active lava lake. The elevation of the bottom platform increases through time, with successive lava lake overflows. After a period of low level between late 2010 and August 2011, the lava lake next came back to its highest level. However, on September 30, 2011, it started a long and progressive fall, reaching ~70 m below the bottom platform in July 2014. This recent evolution of the lava lake, which occurred at the same time period as eruptive events at the neighboring Nyamulagira volcano, was accompanied by a ground subsidence of the bottom platform, leading to the appearance of ring fissures. This ground deformation is restricted to the bottom platform and, hence, suggests a very shallow source for the observed movement. All these changes in the Nyiragongo main crater were recorded by time-series of photographs, allowing the 3D reconstruction of the crater using close-range photogrammetric techniques and, hence, a detailed measurement of the observed changes. The ground subsidence was also recorded by time-series of RADARSAT-2 and CosmoSky-Med SAR interferograms, providing more detailed information on the velocity of deformation. Based on field data and the photogrammetric and InSAR time-series measurements, several hypotheses on the cause(s) of these changes in the Nyiragongo crater are discussed. The present work also highlights the potential of close-range photogrammetry and high-resolution InSAR to study and monitor active volcanoes in Equatorial environment.

  10. Climate variability in south-eastern Australia over the last 1500 years inferred from the high-resolution diatom records of two crater lakes

    NASA Astrophysics Data System (ADS)

    Barr, Cameron; Tibby, John; Gell, Peter; Tyler, Jonathan; Zawadzki, Atun; Jacobsen, Geraldine E.

    2014-07-01

    Climates of the last two millennia have been the focus of numerous studies due to the availability of high-resolution palaeoclimate records and the occurrence of divergent periods of climate, commonly referred to as the ‘Medieval Climatic Anomaly' and ‘The Little Ice Age'. The majority of these studies are centred in the Northern Hemisphere and, in comparison, the Southern Hemisphere is relatively under-studied. In Australia, there are few high-resolution, palaeoclimate studies spanning a millennium or more and, consequently, knowledge of long-term natural climate variability is limited for much of the continent. South-eastern Australia, which recently experienced a severe, decade-long drought, is one such region. Results are presented of investigations from two crater lakes in the south-east of mainland Australia. Fluctuations in lake-water conductivity, a proxy for effective moisture, are reconstructed at sub-decadal resolution over the past 1500 years using a statistically robust, diatom-conductivity transfer function. These data are interpreted in conjunction with diatom autecology. The records display coherent patterns of change at centennial scale, signifying that both lakes responded to regional-scale climate forcing, though the nature of that response varied between sites due to differing lake morphometry. Both sites provide evidence for a multi-decadal drought, commencing ca 650 AD, and a period of variable climate between ca 850 and 1400 AD. From ca 1400-1880 AD, coincident with the timing of the ‘Little Ice Age', climates of the region are characterised by high effective moisture and a marked reduction in inter-decadal variability. The records provide context for climates of the historical period and reveal the potential for more extreme droughts and more variable climate than that experienced since European settlement of the region ca 170 years ago.

  11. Oxygen isotopes as tracers of tektite source rocks: An example from the Ivory Coast tektites and Lake Bosumtwi Crater

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Koeberl, Christian; Chamberlain, C. Page

    1993-01-01

    Oxygen isotope studies of tektites and impact glasses provide an important tool to help in identifying the target lithologies for terrestrial impacts, including the K-T boundary impact. However, such studies may be complicated by modification of the original oxygen isotope values of some source rocks during the tektite formation process either by vapor fractionation or incorporation of meteoric water. To further investigate the relationship between the oxygen isotopic composition of tektites and their source rocks, Ivory Coast tektites and samples of impact glasses and bedrock lithologies from the Bosumtwi Crater in Ghana--which is widely believed to be the source crater for the Ivory Coast tektites--were studied. Our preliminary results suggest that the phyllites and metagraywackes from the Bosumtwi Crater were the predominant source materials for the impact glasses and tektites and that no significant oxygen isotope modification (less than 1 percent delta(O-18)) took place during impact melting. This contrasts with previous studies of moldavites and Australasian tektites and their sedimentary source materials which suggests a 4 to 5 percent lowering of delta(O-18) due to meteoric water incorporation during impact melting.

  12. Limnologic Analysis of Gusev Crater Paleolake, Mars

    NASA Astrophysics Data System (ADS)

    Grin, Edmond A.; Cabrol, Nathalie A.

    1997-12-01

    The survey of the hydrogeologic system formed by Gusev crater and Ma'adim Vallis (Aeolis subquadrangle of Mars) points out evidence for the existence of an ice-covered lake in Gusev crater. A first lake was formed by the drainage of the aquifer in the region surrounding Gusev before the entry of Ma'adim Vallis in the crater. The existence of a former lake in Gusev is deduced from the morphology of the Ma'adim delta. Its comparison with terrestrial Antarctic analogs argues for the presence of an ice-covered lake in Gusev at the time that the southern part of the crater's rampart was breached by Ma'adim first release, and for a subice-lacustrine construction of the valley's delta. Our survey shows that Ma'adim Vallis may have entered Gusev crater as late as Late Hesperian/Early Amazonian as part of a second lake episode. The relationship between the variation of the Gusev lake water-level, the volume of the lake, and the surface of the lake bed is established by our bathymetric model. The elevation of the former lake is deduced from the elevation of the mesa-like structures in the delta of Ma'adim Vallis. Furthermore, the correlation of the crater frequency of Gusev rampart with Mars' stratigraphic age shows that lakes may have occupied Gusev crater over a period of time covering 2 Gyrs., from the formation of the crater to the last episode of water release from Ma'adim Vallis. Though it is most likely that the lake was episodical, the recurrence of abundant water in Gusev crater makes this site a high priority for missions, either for martian resource exploration, or for the search of life.

  13. Microbial Fe cycling and mineralization in sediments of an acidic, hypersaline lake (Lake Tyrell, Victoria, Australia)

    NASA Astrophysics Data System (ADS)

    Roden, E. E.; Blöthe, M.; Shelobolina, E.

    2009-12-01

    Lake Tyrrell is a variably acidic, hypersaline, Fe-rich lake located in Victoria, Australia. Terrestrial acid saline lakes like Lake Tyrrell may be analogs for ancient Martian surface environments, as well as possible extant subsurface environments. To investigate the potential for microbial Fe cycling under acidic conditions and high salt concentration, we collected sediment core samples during three field trips between 2006 and 2008 from the southern, acidic edge of the lake. Materials from the cores were used for chemical and mineralogical analyses, as well as for molecular (16S rRNA genes) and culture-based microbiological studies. Near-surface (< 1 m depth) pore fluids contained low but detectable dissolved oxygen (ca. 50 uM), significant dissolved Fe(II) (ca. 500 uM), and nearly constant pH of around 4 - conditions conducive to enzymatic Fe(II) oxidation. High concentrations of Fe(III) oxides begin accumulate at a depth of ca. 10 cm, and may reflect the starting point for formation of massive iron concretions that are evident at and beneath the sediment surface. MPN analyses revealed low (10-100 cells/mL) but detectable populations of aerobic, halophilic Fe(II)-oxidizing organisms on the sediment surface and in the near-surface ground water. With culture-dependent methods at least three different halotolerant lithoautotrophic cultures growing on Fe(II), thiosulfate, or tetrathionate from different acidic sites were obtained. Analysis of 16S rRNA gene sequences revealed that these organisms are similar to previous described gamma proteobacteria Thiobacillus prosperus (95%), Halothiobacillus kellyi (99%), Salinisphaera shabanense (95%) and a Marinobacter species. (98%). 16S rRNA gene pyrosequencing data from two different sites with a pH range between 3 and 4.5 revealed a dominance of gamma proteobacteria. 16S rRNA gene pyrosequencing libraries from both cores were dominated by sequences related to the Ectothiorhodospiraceae family, which includes the taxa

  14. A survey of lakes in the Republic of Ireland: hydrochemical characteristics and acid sensitivity.

    PubMed

    Aherne, Julian; Kelly-Quinn, Mary; Farrell, Edward P

    2002-09-01

    In 1997, as part of a national program to determine and map critical loads, a lake survey was carried out in the Republic of Ireland. In total 200 lakes were sampled, which represents approximately 3.3% of the total lake population. The majority of lakes were situated in remote, high-altitude, acid-sensitive areas along the coastal margins of the country. Lake chemistry was dominated by marine inputs. Approximately 50% of the lakes had DOC > 5 mg L-1 due to the presence of organic soils in a large proportion of the catchments. Nonmarine sulfate concentrations were at background levels (< 20 mu eq L-1) in 50% of the lakes. Exceedance of critical load was observed in 7% of the sampled lakes (13 lakes). However, there are uncertainties in the critical load calculations due to the interference of sea salts and organic acids; accurate estimation under such conditions requires long-term lake and deposition chemistry.

  15. Spatial and spectral characterization of acid rain stress in Canadian Shield lakes

    NASA Technical Reports Server (NTRS)

    Marshall, Elizabeth J.; Tanis, Frederick J.

    1989-01-01

    Results from this study demonstrate that a remote sensor can discriminate lake clarity based upon reflection. The basic hypothesis was that seasonal and multiyear changes in lake optical transparency are indicative of sensitivity to acidic deposition. In many acid-sensitive lakes optical transparency is controlled by the amount of dissolved organic carbon (DOC) present. DOC is a strong absorbing, nonscattering material which has the greatest impact at short visible wavelengths, including Thematic Mapper band 1. Acid-sensitive lakes have high concentrations of aluminum which have been mobilized by acidic components contained in the runoff. Aluminum complexing with DOC is considered to be the primary mechanism to account for observed increases in lake transparency in acid-sensitive lakes. Thus seasonal changes in the optical transparency of lakes should provide an indication of the stress due to acid deposition and loading.

  16. Characteristics of acidic lakes in the eastern United States (journal version)

    SciTech Connect

    Landers, D.H.; Eilers, J.M.; Brakke, D.F.; Kellar, P.E.

    1988-01-01

    Acidic lakes are found in many regions of the world and are especially common in those regions of the temperate northern hemisphere that have received high levels of acidic deposition during the last several decades. The National Lake Survey was a one-time fall sampling of lakes in regions of the United States suspected of containing lakes susceptible to acidic deposition. The sample lakes were statistically selected from all lakes identified on medium-scale topographic maps to permit population estimates to be calculated of the characteristics of lakes in the target populations in the regions surveyed. Acidic lakes were defined as those lakes with acid-neutralizing capacity (ANC) < or = 0 (as determined by Gran analysis). This definition is limiting in that only the lakes with no remaining ANC are included. It is clear that lakes with ANC > 0 may be acidic based on pH; however, the rationale for defining other or additional categories of acidic lakes is beyond the scope of the presentation.

  17. Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

    USGS Publications Warehouse

    Nanus, L.; Williams, M.W.; Campbell, D.H.; Tonnessen, K.A.; Blett, T.; Clow, D.W.

    2009-01-01

    The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration 3000 m, with 80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

  18. Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Ming, D. W.; Blake, D. F.; Morris, R. V.; Bish, D. L.; Bristow, T. F.; Crisp, J. A.; Morookian, J. M.; Vaniman. D. T.; Chipera, S. J.; Cavanagh, P. D.; Achilles, C. N.; Fairen, A. G.; Morrison, S. M.; Treiman, A. H.; Downs, R. T.; Farmer, J. D.; Fendrich, K. V.

    2015-01-01

    The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF.

  19. Acid lake in N.Y. gets relief

    NASA Astrophysics Data System (ADS)

    A pond in the Adirondack Mountains of New York State has received a second soothing dose of baking soda. The 21 tons of sodium bicarbonate should moderate the pond's acidic conditions, lethal to fish and other forms of life.Wolf Pond, 25 miles (40 km) north of Saranac Lake, has developed an extremely low pH (4.5) because of acid rain and the runoff of acidic surface water, combined with very little outflow. The pond was first treated with sodium bicarbonate by t h e New York Department of Environmental Conservation in 1984; afterward the pH rose to about 6.2. Fish stocked by local residents have continued to live in the pond, despite the eventual rebound in its acidity.

  20. Plasma osmotic and electrolyte concentrations of largemouth bass from some acidic Florida lakes

    SciTech Connect

    Canfield, D.E. Jr.; Maceina, M.J.; Nordlie, F.G.; Shireman, J.V.

    1985-05-01

    Five acidic clear (pH 3.7-4.9), three acidic colored (pH 4.1-4.6), and three neutral (pH 6.9-7.3) north-central Florida lakes were surveyed in 1983 to determine plasma osmotic and electrolyte concentrations, growth, and coefficients of condition for largemouth bass Micropterus salmoides floridanus. Plasma osmotic concentrations averaged greater than 273 milliosmoles/kg in fish from acidic colored and circumneutral lakes, but averaged less than 269 milliosmoles/kg in four of the acidic clear lakes. Growth and coefficients of condition of largemouth bass > 305 mm total length in the acidic lakes were significantly lower than in the neutral lakes. Reductions in fish growth and condition, however, could be related to either acidic conditions or lake trophic status. 29 references, 3 tables.

  1. Similarities Across Mars: Acidic Fluids at Both Meridiani Planum and Gale Crater in the Formation of Magnesium-Nickel Sulfates

    NASA Technical Reports Server (NTRS)

    Yen, Albert S.; Ming, Douglas W.; Gellert, Ralf; Mittlefehldt, David W.; Vaniman, David T.; Thompson, Lucy M.; Morris, Richard V.; Clark, Benton C.; Arvidson, Raymond

    2016-01-01

    In-situ identification of sulfates at the martian surface by the Mars Exploration Rovers and the Mars Science Laboratory have included calcium sulfates with various states of hydration (gypsum, bassanite, anhydrite), iron sulfates of likely fumarolic origin, massive deposits of iron hydroxysulfates indicative of an acidic history, and minor occurrences of magnesium sulfates. Recent measurements by the Opportunity and Curiosity Alpha Particle X-ray Spectrometers (APXS) have indicated the presence of Ni-substituted Mg-sulfates at the Meridiani Planum and Gale Crater landing sites. The Opportunity rover has traversed nearly 43 km and is currently exploring the impact breccias of the rim of Endeavour crater, near a location where signatures of aqueous alteration have been established from orbit. APXS analyses of subsurface materials excavated by a rover wheel show clear evidence for a Mg(Ni)-sulfate with Mg:Ni (is) approximately 100:1 (molar). On the other side of the planet, Curiosity is continuing its climb up Mount Sharp after driving (is) approximately 13 km since landing. Over the last 4 km of the traverse, there have been multiple chemical analyses of erosionally-resistant nodules and dendritic features in a finely laminated mudstone unit which also indicate Mg(Ni)-sulfate (Mg:Ni (is) approximately 30:1, molar). The geologic settings for the Endeavour rim and the Mount Sharp mudstones are clearly different, but similar formation conditions for these sulfates may be possible. Ni(2+) readily substitutes for Mg(2+) in a variety of geochemical processes due to their comparable ionic radii. The availability of soluble Ni at the time of Mg-sulfate precipitation suggests acidic solutions. The fluids responsible for alteration in the Endeavour rim and for the formation of nodules in Gale mudstones may have had similar chemical characteristics at the time the Mg-sulfates were formed.

  2. Meteorite craters

    NASA Technical Reports Server (NTRS)

    Ivanov, B. A.; Bazilevskiy, A. T.

    1986-01-01

    The origin and formation of various types of craters, both on the Earth and on other planetary bodies, are discussed. Various models are utilized to depict various potential causes of the types and forms of meteorite craters in our solar system, and the geological structures are also discussed.

  3. Metals in crayfish from neutralized acidic and non-acidic lakes

    SciTech Connect

    Bagatto, G.; Alikhan, M.A.

    1987-09-01

    Large amounts of acid forming SO/sub 2/, as well as Cu, Ni and other metals are being continuously released into the environment by mining and smelting activities at Sudbury, Ontario, Canada. Consequently, a number of lakes in this region has become both acid and metal stressed. The addition of basic calcium compounds to acidic ponds and lakes has long been recognized as beneficial, as it contributes to increased fish production and water quality. In addition to increases in pH and alkalinity, such additions may reduce water-dissolved metal concentrations, change water transparency and bring about alterations in species diversity. Neutralization experiments have shown that an increase in water alkalinity and DOC may reduce the acute toxicity of Cu to fish. However, the influence of water quality on metal availability and accumulation has received scant attention. Earlier work showed that tissue metal concentrations in crayfish were related to the distance from the emission site. The purpose of the present study is to compare concentrations of six metals in freshwater crayfish from a neutralized acidic lake and a closely situated non-acidic lake. Various tissue concentrations in crayfish are also examined to determine specific tissue sites for these accumulations.

  4. Determination of the mineral stability field of evolving groundwater in the Lake Bosumtwi impact crater and surrounding areas

    NASA Astrophysics Data System (ADS)

    Loh, Yvonne Sena Akosua; Yidana, Sandow Mark; Banoeng-Yakubo, Bruce; Sakyi, Patrick Asamoah; Addai, Millicent Obeng; Asiedu, Daniel Kwadwo

    2016-09-01

    Conventional graphical techniques, mass balance geochemical modelling, and multivariate statistical methods were jointly applied to hydrogeochemical data of groundwater from the fractured rock aquifer system, and surface water in the Bosumtwi and surrounding areas to reveal evolutionary trends and the characteristics of evolving groundwater in the area. Four clusters distinguished from the Q-mode hierarchical cluster analysis (HCA) comprised three main groundwater associations and one surface water group (lake water). Although both water resources are of low mineralization (TDS < 1000 mg/l), it was observed that the groundwater from the upper catchment with hydrochemical facies dominated by Nasbnd Mgsbnd HCO3-, evolves to Casbnd Mgsbnd and mixed cations HCO3- water types at the lower reaches. The lake water on the other hand is Nasbnd HCO3- water type. Results from principal component analyses (PCA) and other geochemical interpretations distinguished three sources of variations in the hydrochemistry. Saturation indices of possible reactive mineral phases show groundwater undersaturation relative to albite, anorthite, aragonite, barite, calcite, chlorite, chrysotile, dolomite, gypsum, k-felspar and talc, and supersaturation with respect to gibbsite, kaolinite, Ca-montmorillonite and k-mica in the area. The PCA and other geochemical interpretation identify weathering of feldspars and carbonate mineral dissolution as predominantly influencing the hydrochemistry of the groundwater. Hydrolysis of the aluminosilicates causes the groundwater to reach equilibrium with kaolinite. In addition to dissolution of silicates, the chemical composition of the lake water has been influenced by evaporation and consequent carbonate saturation.

  5. Eastern Floor of Holden Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 15 April 2002) The Science Today's THEMIS image covers territory on the eastern floor of Holden Crater, which is located in region of the southern hemisphere called Noachis Terra. Holden Crater is 154 km in diameter and named after American Astronomer Edward Holden (1846-1914). This image shows a mottled surface with channels, hills, ridges and impact craters. The largest crater seen in this image is 5 km in diameter. This crater has gullies and what appears to be horizontal layers in its walls. The Story With its beautiful symmetry and gullies radially streaming down to the floor, the dominant crater in this image is an impressive focal point. Yet, it is really just a small crater within a much larger one named Holden Crater. Take a look at the context image to the right to see just how much bigger Holden Crater is. Then come back to the image strip that shows the mottled surface of Holden Crater's eastern floor in greater detail, and count how many hills, ridges, channels, and small impact craters can be seen. No perfectly smooth terrain abounds there, that's for sure. The textured terrain of Holden Crater has been particularly intriguing ever since the Mars Orbital Camera on the Mars Global Surveyor spacecraft found evidence of sedimentary rock layers there that might have formed in lakes or shallow seas in Mars' ancient past. This finding suggests that Mars may have been more like Earth long ago, with water on its surface. Holden Crater might even have held a lake long ago. No one knows for sure, but it's an exciting possibility. Why? If water was once on the surface of Mars long enough to form sedimentary materials, maybe it was there long enough for microbial life to have developed too. (Life as we know it just isn't possible without the long-term presence of liquid water.) The question of life on the red planet is certainly tantalizing, but scientists will need to engage in a huge amount of further investigation to begin to know the answer. That

  6. Subsurface geology, ancient hydrothermal systems and crater excavation processes beneath Lake Rotomahana: Evidence from lithic clasts of the 1886 AD Rotomahana Pyroclastics

    NASA Astrophysics Data System (ADS)

    Pittari, A.; Briggs, R. M.; Bowyer, D. A.

    2016-03-01

    The craters associated with the 1886 AD phreatomagmatic Rotomahana eruption, Okataina Volcanic Centre, New Zealand, and the near-vent geology are now hidden beneath Lake Rotomahana and its post-eruptive sediment fill. Lithic clasts from the near-vent lithic lapilli ash deposits of the Rotomahana Pyroclastics are used in this study to trace geological and geothermal conditions before the eruption, as well as vent excavation dynamics. Near-vent deposit characteristics were described in the field, representative lithic clasts were documented petrographically, and unaltered clasts were analysed for major and trace element compositions. The majority of the lithic clasts were rhyolites with subordinate ignimbrites and hydrothermally altered clasts, and trace siltstone and silicified clasts. The rhyolites were classified into four petrographic groups according to phenocryst content and assemblage and were more diverse with respect to geochemical compositions. Most of the rhyolite lithics in the Rotomahana Pyroclastics did not match the rhyolite domes exposed subaerially around the lake, but did have affinities with the pre-Matahina caldera Wairua Rhyolite, and potentially other older non-exposed domes. Ignimbrites most likely correlated either to the Matahina ignimbrite or older non-exposed units. Hydrothermally altered rhyolite and ignimbrite lithic clasts are common and suggest that there has been a long-lived hydrothermal system in this sector, possibly dating back to early activity of the Okataina Volcanic Centre. The diversity in lithic types indicate a spatial variation in country rock lithology and strength, which probably contributed to the vent position and morphology along the Rotomahana fissure.

  7. Sub-meter desiccation crack patterns imaged by Curiosity at Gale Crater on Mars shed additional light on former lakes evident from examined outcrops

    NASA Astrophysics Data System (ADS)

    Hallet, B.; Sletten, R. S.; Mangold, N.; Oehler, D. Z.; Williams, R. M. E.; Bish, D. L.; Heydari, E.; Rubin, D. M.; Rowland, S. K.

    2015-12-01

    Small-scale desiccation crack patterns (mudcrack-like arrays of uniform ~0.1 to 1 m polygonal domains separated by linear or curving cracks in exposed bedding) imaged by Curiosity in Gale Crater, Mars complement a wealth of diverse data obtained from exposures of sedimentary rocks that point to deposition "in fluvial, deltaic, and lacustrine environments" including an "intracrater lake system likely [to have] existed intermittently for thousands to millions of years …"(e.g. Grotzinger et al., 2015, Science, submitted). We interpret these mudcrack-like patterns, found on many of the bedrock exposures imaged by Curiosity, as desiccation cracks that developed either of two ways: 1) at the soft sediment-air interface like common mudcracks, or 2) at or below the sediment-water interface by synaeresis or diastasis (involving differential compaction). In the context of recent studies of terrestrial mudcracks, and cracks formed experimentally in various wet powders as they loose moisture, these desiccation features reflect diverse aspects of the formative environment. If they formed as mudcracks, some of the lakes were shallow enough to permit the recurrent drying and wetting that can lead to the geometric regularity characteristic of several of sets of mudcracks. Moreover, the water likely contained little suspended sediment otherwise the mudcracks would be buried too rapidly for the crack pattern to persist and to mature into regular polygonal patterns. The preservation of these desiccation crack patterns does not require, but does not exclude, deep burial and exhumation. Although invisible from satellite because of their size, a multitude of Mastcam and Navcam images reveals these informative features in considerable detail. These images complement much evidence, mostly from HiRISE data from several regions, suggesting that potential desiccation polygons on larger scales may be more common on the surface of Mars than generally recognized.

  8. Warm Brine Lakes in Craters of Active Mud Volcanoes, Menes Caldera off NW Egypt: Evidence for Deep-Rooted Thermogenic Processes

    NASA Astrophysics Data System (ADS)

    Dupré, S.; Mascle, J.; Foucher, J. P.; Woodside, J. M.; Pierre, C.

    2015-12-01

    The Menes caldera is a fault-controlled depression (~8 km in diameter) at ~3,000 m water depth in the western province of the Nile deep-sea fan off NW Egypt, comprising seven mud volcanoes (MVs) of which two are active. Based on multichannel and chirp seismic data, temperature profiles, and high-resolution bathymetric data collected during several oceanographic expeditions, the present study investigates factors controlling mud volcano morphology, the geometry of feeder channels, and the origin of emitted fluids (Dupré et al. 2014). The active Cheops and Chephren mud volcanoes are 1,500 m wide with subcircular craters at their summits, about 250 m in diameter, generally a few tens of metres deep, and filled with methane-rich muddy brines with temperatures reaching 42 °C and 57 °C respectively. Deployments of CTDs and corers with attached temperature sensors tracked these warm temperatures down to almost 0.5 km depth below the brine lake surface at the Cheops mud volcano, in a feeder channel probably only a few tens of metres wide. Thermogenic processes involve the dissolution of Messinian evaporites by warm fluids likely sourced even deeper, i.e. 1.7 and 2.6 km below the seabed at the Cheops and Chephren MVs respectively, and which ascend along listric faults. Seepage activity appears broadly persistent since the initiation of mud volcanism in the Early Pliocene, possibly accompanied by lateral migration of feeder channels.

  9. Clustering chlorine reactivity of haloacetic acid precursors in inland lakes.

    PubMed

    Zeng, Teng; Arnold, William A

    2014-01-01

    Dissolved organic matter (DOM) represents the major pool of organic precursors for harmful disinfection byproducts, such as haloacetic acids (HAAs), formed during drinking water chlorination, but much of it remains molecularly uncharacterized. Knowledge of model precursors is thus a prerequisite for understanding the more complex whole water DOM. The utility of HAA formation potential data from model DOM precursors, however, is limited due to the lack of comparability to water samples. In this study, the formation kinetics of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two predominant HAA species, were delineated upon chlorination of seventeen model DOM precursors and sixty-eight inland lake water samples collected from the Upper Midwest region of the United States. Of particular interest was the finding that the DCAA and TCAA formation rate constants could be grouped into four statistically distinct clusters reflecting the core structural features of model DOM precursors (i.e., non-β-diketone aliphatics, β-diketone aliphatics, non-β-diketone phenolics, and β-diketone phenolics). A comparative approach built upon hierarchical cluster analysis was developed to gain further insight into the chlorine reactivity patterns of HAA precursors in inland lake waters as defined by the relative proximity to four model precursor clusters. This work highlights the potential for implementing an integrated kinetic-clustering approach to constrain the chlorine reactivity of DOM in source waters.

  10. A screening procedure for identifying acid-sensitive lakes from catchment characteristics.

    PubMed

    Berg, N H; Gallegos, A; Dell, T; Frazier, J; Procter, T; Sickman, J; Grant, S; Blett, T; Arbaugh, M

    2005-06-01

    Monitoring of Wilderness lakes for potential acidification requires information on lake sensitivity to acidification. Catchment properties can be used to estimate the acid neutralizing capacity (ANC) of lakes. Conceptual and general linear models were developed to predict the ANC of lakes in high-elevation (> or = 2170 m) Wilderness Areas in California's Sierra Nevada mountains. Catchment-to-lake area ratio, lake perimeter-to-area ratio, bedrock lithology, vegetation cover, and lake headwater location are significant variables explaining ANC. The general linear models were validated against independently collected water chemistry data and were used as part of a first stage screen to identify Wilderness lakes with low ANC. Expanded monitoring of atmospheric deposition is essential for improving the predictability of lake ANC.

  11. Spatial characterization of acid rain stress in Canadian Shield Lakes. Final report

    SciTech Connect

    Tanis, F.J.; Marshall, E.M.

    1989-03-01

    The lake acidification in Northern Ontario was investigated using LANDSAT TM to sense lake volume reflectance and also to provide important vegetation and terrain characteristics. The purpose of this project was to determine the ability of LANDSAT to assess water quality characteristics associated with lake acidification. Results demonstrate that a remote sensor can discriminate lake clarity based upon reflection. The basic hypothesis is that seasonal and multi-year changes in lake optical transparency are indicative of sensitivity to acidic deposition. In many acid-sensitive lakes optical transparency is controlled by the amount of dissolved organic carbon present. Seasonal changes in the optical transparency of lakes can potentially provide an indication of the stress due to acid deposition and loading.

  12. Weak disruptive selection and incomplete phenotypic divergence in two classic examples of sympatric speciation: cameroon crater lake cichlids.

    PubMed

    Martin, Christopher H

    2012-10-01

    Recent documentation of a few compelling examples of sympatric speciation led to a proliferation of theoretical models. Unfortunately, plausible examples from nature have rarely been used to test model predictions, such as the initial presence of strong disruptive selection. Here I estimated the form and strength of selection in two classic examples of sympatric speciation: radiations of Cameroon cichlids restricted to Lakes Barombi Mbo and Ejagham. I measured five functional traits and relative growth rates in over 500 individuals within incipient species complexes from each lake. Disruptive selection was prevalent in both groups on single and multivariate trait axes but weak relative to stabilizing selection on other traits and most published estimates of disruptive selection. Furthermore, despite genetic structure, assortative mating, and bimodal species-diagnostic coloration, trait distributions were unimodal in both species complexes, indicating the earliest stages of speciation. Long waiting times or incomplete sympatric speciation may result when disruptive selection is initially weak. Alternatively, I present evidence of additional constraints in both species complexes, including weak linkage between coloration and morphology, reduced morphological variance aligned with nonlinear selection surfaces, and minimal ecological divergence. While other species within these radiations show complete phenotypic separation, morphological and ecological divergence in these species complexes may be slow or incomplete outside optimal parameter ranges, in contrast to rapid divergence of their sexual coloration.

  13. Shackleton Crater

    NASA Video Gallery

    This visualization, created using Lunar Reconnaissance Orbiter laser altimeter data, offers a view of Shackleton Crater located in the south pole of the moon. Thanks to these measurements, we now h...

  14. Effects of acidic deposition on in-lake phosphorus availability: a lesson from lakes recovering from acidification.

    PubMed

    Kopáček, Jiří; Hejzlar, Josef; Kaňa, Jiří; Norton, Stephen A; Stuchlík, Evžen

    2015-03-01

    Lake water concentrations of phosphorus (P) recently increased in some mountain areas due to elevated atmospheric input of P rich dust. We show that increasing P concentrations also occur during stable atmospheric P inputs in central European alpine lakes recovering from atmospheric acidification. The elevated P availability in the lakes results from (1) increasing terrestrial export of P accompanying elevated leaching of dissolved organic carbon and decreasing phosphate-adsorption ability of soils due to their increasing pH, and (2) decreasing in-lake P immobilization by aluminum (Al) hydroxide due to decreasing leaching of ionic Al from the recovering soils. The P availability in the recovering lakes is modified by the extent of soil acidification, soil composition, and proportion of till and meadow soils in the catchment. These mechanisms explain several conflicting observations of the acid rain effects on surface water P concentrations.

  15. Effects of acidic deposition on in-lake phosphorus availability: a lesson from lakes recovering from acidification.

    PubMed

    Kopáček, Jiří; Hejzlar, Josef; Kaňa, Jiří; Norton, Stephen A; Stuchlík, Evžen

    2015-03-01

    Lake water concentrations of phosphorus (P) recently increased in some mountain areas due to elevated atmospheric input of P rich dust. We show that increasing P concentrations also occur during stable atmospheric P inputs in central European alpine lakes recovering from atmospheric acidification. The elevated P availability in the lakes results from (1) increasing terrestrial export of P accompanying elevated leaching of dissolved organic carbon and decreasing phosphate-adsorption ability of soils due to their increasing pH, and (2) decreasing in-lake P immobilization by aluminum (Al) hydroxide due to decreasing leaching of ionic Al from the recovering soils. The P availability in the recovering lakes is modified by the extent of soil acidification, soil composition, and proportion of till and meadow soils in the catchment. These mechanisms explain several conflicting observations of the acid rain effects on surface water P concentrations. PMID:25660534

  16. Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains.

    PubMed

    Nanus, L; Williams, M W; Campbell, D H; Tonnessen, K A; Blett, T; Clow, D W

    2009-06-01

    The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration <100 microeq/L, and therefore sensitive to acidic deposition, are located in basins with elevations >3000 m, with <30% of the catchment having northeast aspect and with >80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world. PMID:19544737

  17. Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains.

    PubMed

    Nanus, L; Williams, M W; Campbell, D H; Tonnessen, K A; Blett, T; Clow, D W

    2009-06-01

    The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration <100 microeq/L, and therefore sensitive to acidic deposition, are located in basins with elevations >3000 m, with <30% of the catchment having northeast aspect and with >80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

  18. Palaeoenvironmental Fluctuations Identified by Diatoms, Ostracode, Geochemistry and Sedimentary Facies from a Tropical Crater Lake on Western Mexico

    NASA Astrophysics Data System (ADS)

    Caballero, M.; Rodriguez, A.; Vazquez, G.; Ortega, B.; Lozano, M.; Vilaclara, G.

    2007-05-01

    A ca. 2500 cal. yr record from Santa Maria del Oro (SMO) was studied for its diatoms, ostracodes, magnetic mineralogy, geochemestry, organic matter and carbonate content to document climatic and limnological trends over western Mexico, a site sensitive to the intensity of monsoon circulation and to any latitudinal shifts of the high pressure subtropical cells as it is currently located on a transition zone between the temperate climates of central Mexico highlands and the arid climates of northern Mexico. The sediment sequence (8.8 m) has a chronology is based on 7 AMS dates. The sequence shows an irregular sequence of four distinctive facies (laminations). Data derived from the analysis of easch facies and of modern sediments supports the interpretation that sand and peaty layers are mostly alloctonous in origin while the silty layers (ochre, brown and greenish silt) are mostly autigenic. Ochre layers represent times of anoxic bottom lake conditions favoured by a warmer environment. Long term trends are also present along the sequence. Warm and relatively humid conditions change to a drier climate by ca. AD 600, with the driest and warmest stage recorded at AD 990. This dry period is consistent with records of arid phases at other sites in Mesoamerica. From AD 990 to AD 1260 there is evidence of a sudden transition to warm-humid conditions and dilution of lake water coeval with the Medieval Warm Period. From AD 1260 to AD 1480 climatic conditions were unstable and afterwards the onset of drier climates is recorded until the present. Due to its geographical position, moisture availability fluctuations are responding to atmospheric circulation changes such as latitudinal shifts of the Intertropical Convergence Zone and Subtropical High- Pressure Cells resulting in the strengthening or weakening of the summer monsoon, which is the main moisture source for western Mexico. This sequence records environmental and climatic variability for western central Mexico and

  19. Henry Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Located in Arabia Terra, the crater shown here is known as Henry Crater. Like many other craters on Mars, the interior of Henry Crater is filled with a layered deposit. These materials were brought into the crater sometime after the impact formed the crater. The fine scale of layering can be seen in the right- center portion of the image.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide.

    ERIC Educational Resources Information Center

    Goss, Lisa M.

    2003-01-01

    Introduces a science demonstration on the dissolution of sulfuric oxide emphasizing the concept of acid rain which is an environmental problem. Demonstrates the acidification from acid rain on two lake environments, limestone and granite. Includes safety information. (YDS)

  1. A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide

    NASA Astrophysics Data System (ADS)

    Goss, Lisa M.

    2003-01-01

    A demonstration showing acid rain and lake acidification is described. In this demonstration, SO2 gas is generated in a large graduated cylinder and then dissolved in water droplets from a simple spray bottle. The droplets carry the acid into simulated lakes, one of which includes solid CaCO3 to mimic limestone's natural buffering capacity.

  2. Thermal and trophic stability of deeper Maine lakes in granite waterhsheds implacted by acid deposition

    SciTech Connect

    Stauffer, R.E.; Wittchen, B.D. )

    1990-09-01

    Acid deposition can lead to lake and watershed acidification, increases in lake transparency, and reduction in thermal stability and hypolimnetic oxygen deficits. On the basis of lake surveys during August-September 1985, we determined to what extent the deeper (maximum depth z{sub m}{gt}17 m) Maine lakes in acid-sensitive granitic watersheds have registered changes in temperature and oxygen stratification, as compared to 1938-1942, when G.P. Cooper performed the earliest scientific surveys of the state's lakes. After correcting for small but geographically consistent interannual differences in summer hypolimnetic temperatures related to spring turnover, and weather-dependent differences in mixed layer depth, there has been no significant change in thermal stratification in these Maine lakes over approximately 43 years. On the basis of specific historical contrasts in the late summer metalimnetic, hypolimnetic, and bathylimnetic oxygen concentrations there has been no significant change in lake trophic state or transparency.

  3. Catchment and atmospheric effects on acidity of lakes in the northeastern United States

    SciTech Connect

    Davis, R.B.; Anderson, D.S.; Rhodes, T.E.

    1995-06-01

    Sedimentary evidence from 12 lakes in northeastern United States reveals that both catchment and atmospheric processes have caused changes in lake acidity. Diatom remains indicate pH 5.2 to 5.8 (one lake 6.8) for one to two centuries before impacts on the catchment by Euro-americans. These low-alkalinity lakes were very sensitive to altered fluxes of base cations and acids. Several lakes increased in pH by 0.2 to 0.6 unit in the 1800s and early 1900s when their catchments were logged. Re-acidification of some of the lakes was initially due to forest succession. Older sediment from one of the lakes also shows alkalization by natural disturbance, and acidification paralleling forest succession. However, much of the recent acidification, to uniquely low levels by the 1970s is due to high sulfur deposition.

  4. Layers in Terby Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-407, 30 June 2003

    Whether on Earth or Mars, sedimentary rocks provide a record of past environments. Of course, it is difficult to read that record without being able to visit the site. However, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has revealed hundreds of locales on Mars at which sedimentary rocks are exposed at the surface. Terby Crater exhibits hundreds of layers of similar thickness and physical properties--some have speculated these may be the record of an ancient lake or sea. This MOC image shows some of the layer outcrops in Terby Crater. Fans of debris have eroded from the steep, layered slopes in some places. This picture covers an area 3 km (1.9 mi) wide near 27.5oS, 285.7oW. The image is illuminated from the upper left and was obtained in June 2003.

  5. Oudemans Crater

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image of the interior of Oudemans Crater was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 1800 UTC (1:00 p.m. EDT) on October 2, 2006, near 9.8 degrees south latitude, 268.5 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across.

    Oudemans Crater is located at the extreme western end of Valles Marineris in the Sinai Planum region of Mars. The crater measures some 124 kilometers (77 miles) across and sports a large central peak.

    Complex craters like Oudemans are formed when an object, such as an asteroid or comet, impacts the planet. The size, speed and angle at which the object hits all determine the type of crater that forms. The initial impact creates a bowl-shaped crater and flings material (known as ejecta) out in all directions along and beyond the margins of the bowl forming an ejecta blanket. As the initial crater cavity succumbs to gravity, it rebounds to form a central peak while material along the bowl's rim slumps back into the crater forming terraces along the inner wall. If the force of the impact is strong enough, a central peak forms and begins to collapse back into the crater basin, forming a central peak ring.

    The uppermost image in the montage above shows the location of CRISM data on a mosaic taken by the Mars Odyssey spacecraft's Thermal Emission Imaging System (THEMIS). The CRISM data was taken inside the crater, on the northeast slope of the central peak.

    The lower left image is an infrared false-color image that reveals several distinctive deposits. The center of the image holds a ruddy-brown deposit that appears to correlates with a ridge running southwest to northeast. Lighter, buff-colored deposits occupy low areas interspersed within the ruddy-brown deposit. The southeast corner holds small hills that form part of the central peak complex.

    The lower right image shows spectral

  6. A New Two-phase Flow Model Applied to the 2007 Crater Lake Break-out Lahar, Mt. Ruapehu, New Zealand

    NASA Astrophysics Data System (ADS)

    Sheridan, M. F.; Cordoba, G.; Pitman, E.; Cronin, S. J.; Procter, J.

    2010-12-01

    The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, is a complex but well-characterized natural debris flow that follows an intricate course over an array of topographic features (see Manville et al., this conference). Detailed digital terrain data (DEM) and accurate flow characterization allow us to test our computational model with an unusually high level of control for such a large natural flood wave. The new two-phase flow code is imbedded within the TITAN2D framework (Patra et al. 2005) that is widely used in hazard assessment for both dry (granular) and wet (debris flow) flows (Murcia et al., 2010). Because TITAN2D is actually valid for dry flows (avalanches) we developed a new two-phase model based on balance laws for mass and momentum for each phase. The granular material is assumed to obey a Coulomb constitutive relation and the fluid is assumed to be inviscid. The Darcy-Weisbach formulation is used to account for bed friction, and a phenomenological drag coefficient mediates the momentum exchange between phases. The resulting system of 6 partial differential equations are depth averaged and correspond to the Savage and Hutter model in the limit of no fluid, and to the typical shallow water solutions (Ortiz, et al., 2005) for pure water. This model is capable of simulating particle volumetric fractions as dilute as 0.001 and as concentrated as 0.55. To confirm the usefulness of the new code for complex flows we used data from four observation stations at Ruapehu located at runout distances of 2 km, 5 km, 7 km and 9 km. The specific flow data that we compare with the model outcomes include: 1) arrival time of the flood front, 2) maximum flood depth, and 3) flow velocity. The computed values for these flow characteristics are all within about ± 10% of the observed figures. References: Manville, V., et al., 2010, Anatomy of a basin break-out flood: The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, this conference. Murcia, H

  7. The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Karlstrom, Leif; Wright, Heather M.; Bacon, Charles R.

    2015-02-01

    The pattern of eruptions at long-lived volcanic centers provides a window into the co-evolution of crustal magma transport, tectonic stresses, and unsteady magma generation at depth. Mount Mazama in the Oregon Cascades has seen variable activity over the last 400 ky, including the 50 km3 climactic eruption at ca. 7.7 ka that produced Crater Lake caldera. The physical mechanisms responsible for the assembly of silicic magma reservoirs that are the precursors to caldera-forming eruptions are poorly understood. Here we argue that the spatial and temporal distribution of geographically clustered volcanic vents near Mazama reflects the development of a centralized magma chamber that fed the climactic eruption. Time-averaged eruption rates at Mount Mazama imply an order of magnitude increase in deep magma influx prior to the caldera-forming event, suggesting that unsteady mantle melting triggered a chamber growth episode that culminated in caldera formation. We model magma chamber-dike interactions over ∼50 ky preceding the climactic eruption to fit the observed distribution of surface eruptive vents in space and time, as well as petrologically estimated deep influx rates. Best fitting models predict an expanding zone of dike capture caused by a growing, oblate spheroidal magma chamber with 10-30 MPa of overpressure. This growing zone of chamber influence causes closest approaching regional mafic vent locations as well as more compositionally evolved Mazama eruptions to migrate away from the climactic eruptive center, returning as observed to the center after the chamber drains during the caldera-forming eruption.

  8. The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

    USGS Publications Warehouse

    Karlstrom, Leif; Wright, Heather M.; Bacon, Charles R.

    2015-01-01

    The pattern of eruptions at long-lived volcanic centers provides a window into the co-evolution of crustal magma transport, tectonic stresses, and unsteady magma generation at depth. Mount Mazama in the Oregon Cascades has seen variable activity over the last 400 ky, including the 50 km3 climactic eruption at ca. 7.7 ka that produced Crater Lake caldera. The physical mechanisms responsible for the assembly of silicic magma reservoirs that are the precursors to caldera-forming eruptions are poorly understood. Here we argue that the spatial and temporal distribution of geographically clustered volcanic vents near Mazama reflects the development of a centralized magma chamber that fed the climactic eruption. Time-averaged eruption rates at Mount Mazama imply an order of magnitude increase in deep magma influx prior to the caldera-forming event, suggesting that unsteady mantle melting triggered a chamber growth episode that culminated in caldera formation. We model magma chamber–dike interactions over ∼50 ky preceding the climactic eruption to fit the observed distribution of surface eruptive vents in space and time, as well as petrologically estimated deep influx rates. Best fitting models predict an expanding zone of dike capture caused by a growing, oblate spheroidal magma chamber with 10–30 MPa of overpressure. This growing zone of chamber influence causes closest approaching regional mafic vent locations as well as more compositionally evolved Mazama eruptions to migrate away from the climactic eruptive center, returning as observed to the center after the chamber drains during the caldera-forming eruption.

  9. Composition of Humic Acids of the Lake Baikal Sediments

    NASA Astrophysics Data System (ADS)

    Vishnyakova, O.; Chimitdorzhieva, G.; Andreeva, D.

    2012-04-01

    Humic substances are the final stage of the biogeochemical transformation of organic matter in the biosphere. Its natural compounds are found not only in soil, peat, coal, and sediments of basins. Chemical composition and properties of humic substances are determined by the functioning of the ecosystem as a whole. Therefore the study of the unique Lake Baikal sediments can provide information about their genesis, as well as the processes of organic matter transformation. For this purpose, preparations of humic acids (HA) were isolated by alkaline extraction method. The composition of HA was investigated by the elemental analyzer CHNS/O PerkinElmer Series II. Various located sediments of the Lake Baikal were the objects of the study: 1 - Chivyrkuisky Bay, 2 - Kotovo Bay, 3 - Selenga river delta near Dubinino village, 4 - Selenga river delta near Murzino village. Data on the elemental composition of HA in terms of ash-free portion show that the carbon content (CC) is of 50-53% with a maximum value in a sample 3, and minimum - in a sample 2. Such values are characteristic also for the soils with low biochemical activity. The hydrogen content is of 4,2-5,3%, a maximum value is in a sample 1. Data recalculation to the atomic percentages identified following regularities. The CC of HA is of 35-39 at. %. Hydrogen content is of 37-43 at. %. According to the content of these elements investigated substances are clearly divided into two groups: HA of the sediments of the Lake Baikal and river Selenga delta. The magnitude of the atomic ratio H/C can be seen varying degrees of condensation of the molecules of humic acids. The high atomic ratio H/C in HA of the former group indicates the predominance of aliphatic structures in the molecules. Humic acids of the later group are characterized by a low value H/C (<1), suggesting a large proportion of aromatic components in HA composition. In sediments of the Selenga river delta there is an addition of organic matter of terrigenous

  10. Authentication controversies and impactite petrography of the New Quebec Crater

    NASA Astrophysics Data System (ADS)

    Marvin, Ursula B.; Kring, David A.

    1992-12-01

    The literature reports that led to the current acceptance of New Quebec Crater (Chubb Crater) as an authentic impact crater are reviewed, and it is noted that, for reasons that are not entirely clear, a meteoritic origin for the New Quebec Crater achieved wider acceptance at an earlier data than for the Lake Bosumtwi Crater, for which petrographic and chemical evidence is more abundant and compelling. The petrography of two impact melt samples from the New Quebec Crater was investigated, and new evidence is obtained on the degrees of shock metamorphism affecting the accessory minerals such as apatite, sphene, magnetite, and zircon.

  11. Authentication controversies and impactite petrography of the New Quebec Crater

    NASA Technical Reports Server (NTRS)

    Marvin, Ursula B.; Kring, David A.

    1992-01-01

    The literature reports that led to the current acceptance of New Quebec Crater (Chubb Crater) as an authentic impact crater are reviewed, and it is noted that, for reasons that are not entirely clear, a meteoritic origin for the New Quebec Crater achieved wider acceptance at an earlier data than for the Lake Bosumtwi Crater, for which petrographic and chemical evidence is more abundant and compelling. The petrography of two impact melt samples from the New Quebec Crater was investigated, and new evidence is obtained on the degrees of shock metamorphism affecting the accessory minerals such as apatite, sphene, magnetite, and zircon.

  12. Characteristics of three acidic lakes in Kejimkujik National Park, Nova Scotia, Canada.

    PubMed

    Kerekes, J; Freedman, B

    1989-01-01

    This report summarizes a study of the chemical and biological characteristics of three oligotrophic lakes located in a region that receives a moderately acidic precipitation (mean annual pH 4.5-4.6), and a sulfate deposition of about 20 kg/ha/yr. The two brownwater lakes are relatively acidic (pH 4.5 and 4.8), and much of their acidity is attributable to organic anions. The brownwater lakes also have a large concentration of aluminum and iron, but these are bound to dissolved organic matter and are relatively non-toxic to biota. Average phytoplankton production was largest in the clearwater lake. This was due to its relatively deep euphotic zone, since the average unit-volume productivity did not differ much among the lakes. In fact, productivity at light optimum was largest in the most acidic brownwater lake, probably because of its larger phosphorus concentration. The clearwater lake had extensive macrophyte vegetation, which covered its bottom to a depth of 6.5 m. In the brownwater lakes, macrophytes were confined to shallow nearshore water because of the limited water transparency. Zooplankton density and biomass were largest in the most acidic brownwater lake, probably because of allochthonous organic particulates and little fish predation. Benthic invertebrates were abundant in all three lakes, and were dominated by insects, especially Chironomids. Lakes in the study area appear to be sustaining fish populations at more acidic pHs than elsewhere. This may be due to the large concentration of dissolved organic matter in many lakes, which complexes and partially detoxifies metals such as aluminum.

  13. Physical and chemical limnological study of an acid mine lake in Sullivan County, Indiana

    SciTech Connect

    Broomall, P.A.

    1992-01-01

    Southwestern Indiana has numerous lakes developed in abandoned coal mine spoils which support recreational sports fisheries. Some lakes, due to exposure to acid mine drainage from coal wastes and pyritic spoils, are unsuitable habitats for fisheries development. This study examines a publicly owned acid mine lake with an area of approximately 51 ha, following reclamation and elimination of acid producing areas in its drainage basin. Fifteen physico-chemical sample collections were made over a thirteen month period (1991--1992). Parameters sampled included pH, total acidity, iron, manganese, and aluminum. Comparisons were made to historic pre-reclamation water quality data and to established models of acid mine lake recovery. Due to the local topography and exposure to prevailing winds, the lake was generally well mixed throughout the study. Virtually no summer stratification was found, but typical winter season stratification occurred. The water column was well oxygenated throughout the study. Secchi disk transparency varied from 2.5 m to clear to lake bottom (6 m). This study found no significant change in lake water pH (2.9--3.0 to 3.0--3.2 s.u.) since reclamation activities in 1988. However, changes in total acidity and total metal concentrations had occurred since reclamation which suggested that the lake was in early recovery stages. No trends in water quality improvement were determined which could assist in planning toward the eventual establishment of a sports fishery.

  14. Acid precipitation effects on algal productivity and biomass in Adirondack Mountain lakes

    SciTech Connect

    Hendrey, G.R.

    1982-12-01

    Relationships between phytoplankton communities and lake acidity in three Adirondack Mountain lakes were studied at Woods Lake (pH ca. 4.9), Sagamore Lake (pH ca. 5.5), and Panther Lake (pH ca. 7.0). Species numbers decrease with increasing acidity. Patterns of increasing biomass and productivity in Woods Lake may be atypical of similar oligotrophic lakes in that they develop rather slowly to maxima six weeks after ice-out, instead of occurring very close to ice-out. Contributions of netplankton, nannoplankton and ultraplankton to productivity per m/sup 2/ show that the smaller plankton are relatively more important in the more acid lakes. This pattern could be determined by nutrient availability (lake acidification is suspected of leading to decreased availability of phosphorus). This was consistent with a hypothesis that microbial heterotrophic activity is reduced with increasing acidity, but the smaller phytoplankton may be more leaky at low pH. 11 references, 2 tables.

  15. Impact Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Today marks the 45th anniversary of the dawn of the Space Age (October 4, 1957). On this date the former Soviet Union launched the world's first satellite, Sputnik 1. Sputnik means fellow traveler. For comparison Sputnik 1 weighed only 83.6 kg (184 pounds) while Mars Odyssey weighs in at 758 kg (1,671 pounds).

    This scene shows several interesting geologic features associated with impact craters on Mars. The continuous lobes of material that make up the ejecta blanket of the large impact crater are evidence that the crater ejecta were fluidized upon impact of the meteor that formed the crater. Volatiles within the surface mixed with the ejecta upon impact thus creating the fluidized form. Several smaller impact craters are also observed within the ejecta blanket of the larger impact crater giving a relative timing of events. Layering of geologic units is also observed within the large impact crater walls and floor and may represent different compositional units that erode at variable rates. Cliff faces, dissected gullies, and heavily eroded impact craters are observed in the bottom half of the image at the terminus of a flat-topped plateau.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS

  16. Perfluorinated acids in air, rain, snow, surface runoff, and lakes: relative importance of pathways to contamination of urban lakes.

    PubMed

    Kim, Seung-Kyu; Kannan, Kurunthachalam

    2007-12-15

    Concentrations of perfluorinated acids (PFAs) were measured in various environmental matrices (air, rain, snow, surface runoff water, and lake water) in an urban area, to enable identification of sources and pathways of PFAs to urban water bodies. Total PFA concentrations ranged from 8.28 to 16.0 pg/ m3 (mean 11.3) in bulk air (sum of vapor and particulate phases), 0.91 to 13.2 ng/L (6.19) in rainwater, 0.91 to 23.9 ng/L (7.98) in snow, 1.11-81.8 ng/L (15.1 ng/L) in surface runoff water (SRW), and 9.49 to 35.9 ng/L (21.8) in lake water. Perfluorooctanoic acid (PFOA) was the predominant compound, accounting for > 35% of the total PFA concentrations, in all environmental matrices analyzed. Concentrations and relative compositions of PFAs in SRW were similar to those found for urban lakes. SRW contributes to contamination by PFOA in urban lakes. The measured concentration ratios of FTOH to PFOA in air were 1-2 orders of magnitude lower than the ratios calculated based on an assumption of exclusive atmospheric oxidation of FTOHs. Nevertheless, the mass balance analysis suggested the presence of an unknown input pathway that could contribute to a significant amount of total PFOA loadings to the lake. Flux estimates of PFOA at the air-water interface in the urban lake suggest net volatilization from water.

  17. Cycling of iron and trace metals in the sediments of acidic lakes

    SciTech Connect

    Gubala, C.P.

    1988-01-01

    This study focused on four lakes receiving acidic deposition located in the Adirondack Park, New York, U.S.A. The biogeochemistry of sediments and interstitial water along a depth transect in Big Moose, Lake was examined by chemical analysis of sediment and pore water. Solid phases of iron, manganese, aluminum, lead and zinc were quantified, using a sequential chemical extraction process. {sup 210}Pb dating, and equilibrium and diffusion transport modeling were used to assess the degree of post-depositional reprocessing of these metals. The sediment chemistry of Dart Lake, Lake Rondaxe and South Lake, were compared to the sediment processes observed in Big Moose Lake to assess inter-lake variability.

  18. Parent Body Influences on Amino Acids in the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Callahan, M. P.; Dworkin, J. P.; Elsila, J. E.; Herd, C. D. K.

    2010-01-01

    The Tagish Lake meteorite is a primitive C2 carbonaceous chondrite with a mineralogy, oxygen isotope, and bulk chemical. However, in contrast to many CI and CM carbonaceous chondrites, the Tagish Lake meteorite was reported to have only trace levels of indigenous amino acids, with evidence for terrestrial L-amino acid contamination from the Tagish Lake meltwater. The lack of indigenous amino acids in Tagish Lake suggested that they were either destroyed during parent body alteration processes and/or the Tagish Lake meteorite originated on a chemically distinct parent body from CI and CM meteorites where formation of amino acids was less favorable. We recently measured the amino acid composition of three different lithologies (11h, 5b, and 11i) of pristine Tagish Lake meteorite fragments that represent a range of progressive aqueous alteration in order 11h < 5b < 11i as inferred from the mineralogy, petrology, bulk isotopes, and insoluble organic matter structure. The distribution and enantiomeric abundances of the one- to six-carbon aliphatic amino acids found in hot-water extracts of the Tagish Lake fragments were determined by ultra performance liquid chromatography fluorescence detection and time of flight mass spectrometry coupled with OPA/NAC derivatization. Stable carbon isotope analyses of the most abundant amino acids in 11h were measured with gas chromatography coupled with quadrupole mass spectrometry and isotope ratio mass spectrometry.

  19. Paleolimnological Diatom Studies of Acidification of Lakes by Acid Rain: An Application of Quaternary Science

    NASA Astrophysics Data System (ADS)

    Davis, Ronald B.

    The methods of Quaternary paleoecology have proven useful for understanding the effects of anthropogenic acid deposition on lakes. The pH history of lakes has been inferred from diatom remains in 210Pb dated cores of sediment. In several of these studies, the cores have also been analysed for chrysophyte scales, trace metals (Pb, Zn, V, Cu), soot, and polycyclic aromatic hydrocarbons. Combined with historical studies of watershed vegetation and disturbance, these approaches have produced important insights relating to the effects on lakes of acid deposition: (1) certain clear water lakes with present pH 4.3-5.0 have rapidly acidified in recent decades; (2) these lakes were acidic (pH 5.0-6.4) prior to the acidification; (3) the most likely cause of the acidification is acid deposition; (4) the acidification began decades after high levels of acid deposition had been reached; and (5) in certain lakes acidification may have caused a marked decrease in humics, reducing the availability of organic ligands for 'detoxification' of metal ions (e.g. Al) mobilized by acidification. Diatom analyses have also revealed long term lake acidification in Late-glacial and Holocene time before the Industrial Revolution. This acidification is much slower than the modern acidification. The present pHs in anthropogenically acidified lakes are unprecedentedly low.

  20. Kuiper Crater

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The Mariner 10 Television-Science Team has proposed the name 'Kuiper' for this very conspicuous bright Mercury crater (top center) on the rim of a larger older crater. Prof. Gerard P. Kuiper, a pioneer in planetary astronomy and a member of the Mariner 10 TV team, died December 23, 1973, while the spacecraft was enroute to Venus and Mercury. Mariner took this picture (FDS 27304) from 88,450 kilometers (55,000 miles) some 2 1/2 hours before it passed Mercury on March 29. The bright-floored crater, 41 kilometers (25 miles) in diameter, is the center of a very large bright are which could be seen in pictures sent from Mariner 10 while Mercury was more than two million miles distant. The larger crater is 80 kilometers (50 miles) across.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  1. Crater Comparison

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    These two craters show the two types of crater interiors found on Mars -- original and modified. The crater on the right has its original bowl shape. The crater of the left has had its interior modified by an infilling of lava.

    Image information: VIS instrument. Latitude 27.6, Longitude 194.5 East (165.5 West). 37 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  2. Spatial characterization of acid rain stress in Canadian Shield lakes. Progress report, 1 August 1985-1 February 1986

    SciTech Connect

    Tanis, F.J.

    1986-01-01

    The acidification of lake waters from airborne pollutants is of continental proportions both in North America and Europe. A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forest. The number of lakes affected in northeastern United States and on the Canadian Shield is though to be enormous. The principle objective is to examine how seasonal changes in lake water transparency are related to annual acidic load. Further, the relationship between variations in lake acidification and ecophysical units is being examined. Finally, the utility of Thematic Mapper (TM) based observations to measure seasonal changes in the optical transparency in acid lakes is being investigated.

  3. Lessons from studies of impact crater hydrothermal processes in terrestrial analogs and their implications for impact craters on Mars

    NASA Astrophysics Data System (ADS)

    Newsom, H. E.

    2011-12-01

    Studying hydrothermal processes in terrestrial impact craters as martian analogs has sometimes been fraught with objections, including the Earth's greater abundance of water, the neutral instead of acidic aqueous environments and the composition of the targets. Although recent discoveries have dispelled many objections, some misconceptions remain. For example, the relevance of the Chicxulub crater as a martian analog is sometimes questioned because the target was covered with sediments, including carbonates and sulfates. However the impactites at the Yaxcopoil-1 drill site are derived from the underlying silicate basement. Comparisons can also be difficult because of scale issues, as many terrestrial craters with evidence of hydrothermal activity, e.g. Lonar, Haughton, Ries etc., are smaller than the Martian craters with phyllosilicate signatures (Ehlmann et al., 2010). Summarizing, the results of many studies of terrestrial craters show that: 1) Most terrestrial craters larger than 1.8 km diameter have at least some evidence of aqueous or hydrothermal processes in the form of alteration minerals (e.g., Naumov, 2005). 2) Impact melts in crater fill and ejecta blankets provide heat that can produce hydrothermal alteration if water is available (Newsom, 1980). 3) The uplifted geothermal gradient can be as important a heat source as shock effects. 4) Mineralogical evidence for high-temperature fluids (> 350 oC) is present in the central uplift of the Manson structure, and in the ejecta from the Chicxulub impact, where precipitation of phyllosilicates from hydrothermal fluids has also been described (Newsom et al., 2010). 5) Impact deposits begin hot, but have an extended cooling period during which alteration phases can back react to low temperature phases with corresponding stable isotope signatures. 5) Hydrothermal fluids can travel long distances from their sources (e.g., Chicxulub, Yaxcopoil site) and are often localized to faults or porous breccias (e.g. Sudbury

  4. Effect of atmospheric sulfur pollutants derived from acid precipitation on the benthic dynamics of lakes

    SciTech Connect

    Mitchell, M.J.

    1982-11-01

    Sulfuric acid is a major contributor to acid precipitation in the United States. The relationship of acid precipitation to the sulfur dynamics of three lakes in New York was studied. For South Lake, which has probably been acidified, the sulfur profile in the sediment corresponded to historical changes in anthropogenic sulfur inputs. In all three study lakes, the organic sulfur constituents, which generally have been ignored in limnological investigations, played a major role in sulfur dynamics. The transformations and fluxes of inorganic and organic sulfur differed among the lakes and reflected characteristic abiotic and biotic properties, including productivity parameters. The community structure and secondary production of the invertebrate benthos were ascertained and, for South Lake, were similar to other acidified lakes. The importance of benthic insects on sulfur dynamics was demonstrated. Further studies on sulfur in lakes will enhance the understanding of the role of these anthropogenic inputs on lake systems and permit a more accurate appraisal of the present and future impacts of acidic deposition on water quality. 10 references.

  5. Stable isotope and petrologic evidence for open-system degassing during the climactic and pre-climactic eruptions of Mt. Mazama, Crater Lake, Oregon

    USGS Publications Warehouse

    Mandeville, C.W.; Webster, J.D.; Tappen, C.; Taylor, B.E.; Timbal, A.; Sasaki, A.; Hauri, E.; Bacon, C.R.

    2009-01-01

    Evaluation of the extent of volatile element recycling in convergent margin volcanism requires delineating likely source(s) of magmatic volatiles through stable isotopic characterization of sulfur, hydrogen and oxygen in erupted tephra with appropriate assessment of modification by degassing. The climactic eruption of Mt. Mazama ejected approximately 50 km3 of rhyodacitic magma into the atmosphere and resulted in formation of a 10-km diameter caldera now occupied by Crater Lake, Oregon (lat. 43??N, long. 122??W). Isotopic compositions of whole-rocks, matrix glasses and minerals from Mt. Mazama climactic, pre-climactic and postcaldera tephra were determined to identify the likely source(s) of H2O and S. Integration of stable isotopic data with petrologic data from melt inclusions has allowed for estimation of pre-eruptive dissolved volatile concentrations and placed constraints on the extent, conditions and style of degassing. Sulfur isotope analyses of climactic rhyodacitic whole rocks yield ??34S values of 2.8-14.8??? with corresponding matrix glass values of 2.4-13.2???. ??34S tends to increase with stratigraphic height through climactic eruptive units, consistent with open-system degassing. Dissolved sulfur concentrations in melt inclusions (MIs) from pre-climactic and climactic rhyodacitic pumices varies from 80 to 330 ppm, with highest concentrations in inclusions with 4.8-5.2 wt% H2O (by FTIR). Up to 50% of the initial S may have been lost through pre-eruptive degassing at depths of 4-5 km. Ion microprobe analyses of pyrrhotite in climactic rhyodacitic tephra and andesitic scoria indicate a range in ??34S from -0.4??? to 5.8??? and from -0.1??? to 3.5???, respectively. Initial ??34S values of rhyodacitic and andesitic magmas were likely near the mantle value of 0???. Hydrogen isotope (??D) and total H2O analyses of rhyodacitic obsidian (and vitrophyre) from the climactic fall deposit yielded values ??f -103 to -53??? and 0.23-1.74 wt%, respectively. Values of

  6. Galle Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 19 June 2002) The Science This image is of part of Galle Crater, located at 51.9S, 29.5W. This image was taken far enough south and late enough into the southern hemisphere fall to catch observe water ice clouds partially obscuring the surface. The most striking aspect of the surface is the dissected layered unit to the left in the image. Other areas also appear to have layering, but they are either more obscured by clouds or are less well defined on the surface. The layers appear to be mostly flat lying and layer boundaries appear as topographic lines would on a map, but there are a few areas where it appears that these layers have been deformed to some level. Other areas of the image contain rugged, mountainous terrain as well as a separate pitted terrain where the surface appears to be a separate unit from the mountains and the layered terrain. The Story Galle Crater is officially named after a German astronomer who, in 1846, was the first to observe the planet Neptune. It is better known, however, as the 'Happy Face Crater.' The image above focuses on too small an area of the crater to see its beguiling grin, but you can catch the rocky line of a 'half-smile' in the context image to the right (to the left of the red box). While water ice clouds make some of the surface harder to see, nothing detracts from the fabulous layering at the center left-hand edge of the image. If you click on the above image, the scalloped layers almost look as if a giant knife has swirled through a landscape of cake frosting. These layers, the rugged, mountains near them, and pits on the surface (upper to middle section of the image on the right-hand side) all create varying textures on the crater floor. With such different features in the same place, geologists have a lot to study to figure out what has happened in the crater since it formed.

  7. Erosional modification and gully formation at Meteor Crater, Arizona: Insights into crater degradation processes on Mars

    NASA Astrophysics Data System (ADS)

    Kumar, P. Senthil; Head, James W.; Kring, David A.

    2010-08-01

    Hydrogeological modification of Meteor Crater produced a spectacular set of gullies throughout the interior wall in response to rainwater precipitation, snow melting, and possible groundwater discharge. The crater wall has an exceptionally well-developed centripetal drainage pattern consisting of individual alcoves, channels, and fans. Some of the gullies originate from the rim crest and others from the middle crater wall where a lithologic transition occurs; broad gullies occur along the crater corner radial faults. Deeply incised alcoves are well developed on the soft Coconino Sandstone exposed on the middle crater wall, beneath overlying dolomite. In general, the gully locations are along crater wall radial fractures and faults, which are favorable locales of erosion due to preferential rock breakup from faulting, and groundwater flow/discharge; these structural discontinuities are also the locales where the surface runoff from rain precipitation and snow melting can preferentially flow, causing erosion and crater degradation. Channels are well developed on the talus deposits and alluvial fans on the periphery of the crater floor. Caves exposed on the lower crater level point to percolation of surface runoff and selective discharge through fractures on the crater wall. In addition, lake sediments on the crater floor provide significant evidence of a past pluvial climate, when the water table was higher, and groundwater may have seeped from springs on the crater wall. Although these hydrological processes continue at Meteor Crater today, conditions at the crater are much more arid than they were soon after impact, reflecting a climatic shift. This climate shift and the hydrological modifications observed at Meteor Crater provide insights for landscape sculpturing on Mars during various parts of its history.

  8. Centrifuge impact cratering experiment 5

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Transient crates motions, cratering flow fields, crates dynamics, determining impact conditions from total crater welt, centrifuge quarter-space cratering, and impact cratering mechanics research is documented.

  9. Hydrogeologic comparison of an acidic-lake basin with a neutral-lake basin in the West-Central Adirondack Mountains, New York

    USGS Publications Warehouse

    Peters, N.E.; Murdoch, Peter S.

    1985-01-01

    Two small headwater lake basins that receive similar amounts of acidic atmospheric deposition have significantly different lake outflow pH values; pH at Panther Lake (neutral) ranges from about 4.7 to 7; that at Woods Lake (acidic) ranges from about 4.3 to 5. A hydrologic analysis, which included monthly water budgets, hydrograph analysis, examination of flow duration and runoff recession curves, calculation of ground-water storage, and an analysis of lateral flow capacity of the soil, indicates that differences in lakewater pH can be attributed to differences in the ground-water contribution to the lakes. A larger percentage of the water discharged from the neutral lake is derived from ground water than that from the acidic lake. Ground water has a higher pH resulting from a sufficiently long residence time for neutralizing chemical reactions to occur with the till. The difference in ground-water contribution is attributed to a more extensive distribution of thick till (<3m) in the neutral-lake basin than in the acidic-lake basin; average thickness of till in the neutral-lake basin is 24m whereas that in the other is 2.3m. During the snowmelt period, as much as three months of accumulated precipitation may be released within two weeks causing the lateral flow capacity of the deeper mineral soil to be exceeded in the neutral-lake basin. This excess water moves over and through the shallow acidic soil horizons and causes the lakewater pH to decrease during snowmelt.Two small headwater lake basins that receive similar amounts of acidic atmospheric deposition have significantly different lake outflow pH values; pH at Panther Lake (neutral) ranges from about 4. 7 to 7; that at Woods Lake (acidic) ranges from about 4. 3 to 5. A hydrologic analysis, which included monthly water budgets, hydrograph analysis, examination of flow duration and runoff recession curves, calculation of ground-water storage, and an analysis of lateral flow capacity of the soil, indicates that

  10. The evolution of a mining lake - From acidity to natural neutralization.

    PubMed

    Sienkiewicz, Elwira; Gąsiorowski, Michał

    2016-07-01

    Along the border of Poland and Germany (central Europe), many of the post-mining lakes have formed "an anthropogenic lake district". This study presents the evolution of a mining lake ecosystem (TR-33) based on subfossil phyto- and zooplankton, isotopic data (δ(13)C, δ(15)N), elemental analyses of organic carbon and nitrogen (C/N ratio and TOC) and sedimentological analyses. Recently, lake TR-33 became completely neutralized from acidification and an increase in eutrophication began a few years ago. However, the lake has never been neutralized by humans; only natural processes have influenced the present water quality. From the beginning of the existence of the lake (1920s) to the present, we can distinguish four stages of lake development: 1) very shallow reservoir without typical lake sediments but with a sand layer containing fine lignite particles and very poor diatom and cladoceran communities; 2) very acidic, deeper water body with increasing frequencies of phyto- and zooplankton; 3) transitional period (rebuilding communities of diatoms and Cladocera), meaning a deep lake with benthic and planktonic fauna and flora with wide ecological tolerances; and 4) a shift to circumneutral conditions with an essential increase in planktonic taxa that prefer more fertile waters (eutrophication). In the case of lake TR-33, this process of natural neutralization lasted approximately 23years.

  11. Crater Landslide

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA06088 Crater Landslide

    This landslide occurs in an unnamed crater southeast of Millochau Crater.

    Image information: VIS instrument. Latitude -24.4N, Longitude 87.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  12. Crater Clouds

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA06085 Crater Clouds

    The crater on the right side of this image is affecting the local wind regime. Note the bright line of clouds streaming off the north rim of the crater.

    Image information: VIS instrument. Latitude -78.8N, Longitude 320.0E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  13. Cydonia Craters

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Eroded mesas and secondary craters dot the landscape in this area of the Cydonia Mensae region. The single oval-shaped crater displays a 'butterfly' ejecta pattern, indicating that the crater formed from a low-angle impact.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 32.9, Longitude 343.8 East (16.2 West). 19 meter/pixel resolution.

  14. Crater Highlands, Tanzania

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The Shuttle Radar Topography Mission (SRTM), flown aboard Space Shuttle Endeavour in February 2000, acquired elevation measurements for nearly all of Earth's landmass between 60oN and 56oS latitudes. For many areas of the world SRTM data provide the first detailed three-dimensional observation of landforms at regional scales. SRTM data were used to generate this view of the Crater Highlands along the East African Rift in Tanzania. Landforms are depicted with colored height and shaded relief, using a vertical exaggeration of 2X and a southwestwardly look direction.

    Lake Eyasi is depicted in blue at the top of the image, and a smaller lake occurs in Ngorongoro Crater. Near the image center, elevations peak at 3648 meters (11,968 feet) at Mount Loolmalasin, which is south of Ela Naibori Crater. Kitumbeine (left) and Gelai (right) are the two broad mountains rising from the rift lowlands. Mount Longido is seen in the lower left, and the Meto Hills are in the right foreground.

    Tectonics, volcanism, landslides, erosion and deposition -- and their interactions -- are all very evident in this view. The East African Rift is a zone of spreading between the African (on the west) and Somali (on the east) crustal plates. Two branches of the rift intersect here in Tanzania, resulting in distinctive and prominent landforms. One branch trends nearly parallel the view and includes Lake Eyasi and the very wide Ngorongoro Crater. The other branch is well defined by the lowlands that trend left-right across the image (below center, in green). Volcanoes are often associated with spreading zones where magma, rising to fill the gaps, reaches the surface and builds cones. Craters form if a volcano explodes or collapses. Later spreading can fracture the volcanoes, which is especially evident on Kitumbeine and Gelai Mountains (left and right, respectively, lower center).

    The Crater Highlands rise far above the adjacent savannas, capture moisture from passing air masses

  15. Evidence for Siliceous Deposits Formed by Acid-Sulfate Alteration at Home Plate in Gusev Crater, Mars

    NASA Astrophysics Data System (ADS)

    Morris, R. V.; Ming, D. W.; Gellert, R.; Yen, A. S.; Clark, B. C.; Ruff, S. W.; Graff, T. G.; Arvidson, R. E.; Squyres, S. W.; Science Teams, T.

    2007-12-01

    The Alpha Particle X-ray Spectrometer (APXS) instrument on the Mars Exploration Rover (MER) Spirit measured three targets on or adjacent to Home Plate in Gusev Crater that have unusually high SiO2 concentrations (68 to 91%), unusually low FeO concentrations (1 to 7%, with total Fe as FeO), and unusually high TiO2/FeO ratios (0.2 to 1.2 by weight). Two targets are high albedo soil (Gertrude Weise) exposed by the rover wheels (Kenosha Comets and Lefty Ganote), and one target is a rock (Fuzzy Smith). Kenosha Comets has the highest SiO2 concentration, lowest FeO concentration, and highest TiO2/FeO ratio. Mineralogical evidence from the MER Miniature Thermal Emission Spectrometer (Mini-TES) suggests that high proportions of amorphous (non- crystalline) SiO2 account for the high SiO2 concentration of Gertrude Weise. Mini-TES data were not acquired for Fuzzy Smith. The spectral evidence for amorphous SiO2 includes deep emissivity minima near 9 and 21 microns. Amorphous SiO2 is typically characterized by a shoulder near 8 microns, but the Gertrude Weise spectra are instead characterized by a well-defined emissivity minimum. The difference is attributed to scattering and/or geometric effects. The chemistry of Gertrude Weise and Fuzzy Smith is very similar to that for a tholeiitic basaltic rock altered under acid-sulfate conditions in a fumarolic (hydrothermal) environment on Kilauea Volcano (Hawaii). The terrestrial acid sulfate alteration resulted in compositions having about 62 to 91% SiO2, 1 to 8% FeO, and 0.3 to 5 TiO2/FeO. The SiO2 and TiO2 are passively enriched while all other major elements are removed by leaching. XRD analysis shows that SiO2 and TiO2 are present as amorphous SiO2 (opal-A) and anatase, respectively. Alunite is also present. Thermal emission spectra of the Kilauea rock obtained from its exterior surface and from 500-1000 micron and <150 micron powders derived by grinding and sieving are all characterized by the emissivity features at 8, 9, and 21

  16. Aquatic fulvic acids in microbially based ecosystems: results from two desert lakes in Antarctica

    USGS Publications Warehouse

    McKnight, Diane M.; Aiken, G.R.; Smith, R.L.

    1991-01-01

    These lakes receive very limited input of organic material from the surrounding barren desert, but they sustain algal and bacterial populations under permanent ice cover. One lake has an extensive anoxic zone and high salinities; the other is oxic and has low salinities. Despite these differences, fulvic acids from both lakes had similar elemental compositions, carbon distributions, and amino acid contents, indicating that the chemistry of microbially derived fulvic acvids is not strongly influenced by chemical conditions in the water column. Compared to fulvic acids from other natural waters, these fulvic acids have low C:N atomic ratios (19-25) and low contents of aromatic carbons (5-7% of total carbon atoms); they are most similar to marine fulvic acids. -from Authors

  17. Impact Cratering Calculations

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.

    1997-01-01

    Understanding the physical processes of impact cratering on planetary surfaces and atmospheres as well as collisions of finite-size self-gravitating objects is vitally important to planetary science. The observation has often been made that craters are the most ubiquitous landform on the solid planets and the satellites. The density of craters is used to date surfaces on planets and satellites. For large ringed basin craters (e.g. Chicxulub), the issue of identification of exactly what 'diameter' transient crater is associated with this structure is exemplified by the arguments of Sharpton et al. (1993) versus those of Hildebrand et al. (1995). The size of a transient crater, such as the K/T extinction crater at Yucatan, Mexico, which is thought to be the source of SO,-induced sulfuric acid aerosol that globally acidified surface waters as the result of massive vaporization of CASO, in the target rock, is addressed by our present project. The impact process excavates samples of planetary interiors. The degree to which this occurs (e.g. how deeply does excavation occur for a given crater diameter) has been of interest, both with regard to exposing mantle rocks in crater floors, as well as launching samples into space which become part of the terrestrial meteorite collection (e.g. lunar meteorites, SNC's from Mars). Only in the case of the Earth can we test calculations in the laboratory and field. Previous calculations predict, independent of diameter, that the depth of excavation, normalized by crater diameter, is d(sub ex)/D = 0.085 (O'Keefe and Ahrens, 1993). For Comet Shoemaker-Levy 9 (SL9) fragments impacting Jupiter, predicted excavation depths of different gas-rich layers in the atmosphere, were much larger. The trajectory and fate of highly shocked material from a large impact on the Earth, such as the K/T bolide is of interest. Melosh et al. (1990) proposed that the condensed material from the impact upon reentering the Earth's atmosphere induced. radiative

  18. Cutting Craters

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 12 November 2003

    The rims of two old and degraded impact craters are intersected by a graben in this THEMIS image taken near Mangala Fossa. Yardangs and low-albedo wind streaks are observed at the top of the image as well as interesting small grooves on the crater floor. The origin of these enigmatic grooves may be the result of mud or lava and volatile interactions. Variable surface textures observed in the bottom crater floor are the result of different aged lava flows.

    Image information: VIS instrument. Latitude -15.2, Longitude 219.2 East (140.8 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. Crater Copernicus

    NASA Technical Reports Server (NTRS)

    1999-01-01

    HUBBLE SHOOTS THE MOON in a change of venue from peering at the distant universe, NASA's Hubble Space Telescope has taken a look at Earth's closest neighbor in space, the Moon. Hubble was aimed at one of the Moon's most dramatic and photogenic targets, the 58 mile-wide (93 km) impact crater Copernicus. The image was taken while the Space Telescope Imaging Spectrograph(STIS) was aimed at a different part of the moon to measure the colors of sunlight reflected off the Moon. Hubble cannot look at the Sun directly and so must use reflected light to make measurements of the Sun's spectrum. Once calibrated by measuring the Sun's spectrum, the STIS can be used to study how the planets both absorb and reflect sunlight.(upper left)The Moon is so close to Earth that Hubble would need to take a mosaic of 130 pictures to cover the entire disk. This ground-based picture from Lick Observatory shows the area covered in Hubble's photomosaic with the WideField Planetary Camera 2..(center)Hubble's crisp bird's-eye view clearly shows the ray pattern of bright dust ejected out of the crater over one billion years ago, when an asteroid larger than a mile across slammed into the Moon. Hubble can resolve features as small as 600 feet across in the terraced walls of the crater, and the hummock-like blanket of material blasted out by the meteor impact.(lower right)A close-up view of Copernicus' terraced walls. Hubble can resolve features as small as 280 feet across.

  20. Buried Craters

    NASA Technical Reports Server (NTRS)

    2005-01-01

    26 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two circular features on the plains of northern Utopia. A common sight on the martian northern plains, these rings indicate the locations of buried impact craters.

    Location near: 65.1oN, 261.2oW Image width: 2 km (1.2 mi) Illumination from: lower left Season: Northern Summer

  1. Biomass and production of amphipods in low alkalinity lakes affected by acid precipitation.

    PubMed

    France, R L

    1996-01-01

    Population biomass and production of the amphipod Hyalella azteca (Saussure) were found to be related to alkalinity (ranging from 0.2 to 58.1 mg liter(-1)) in 10 Canadian Shield lakes in south-central Ontario. Biomass and production of amphipods in the two lakes characterized by spring depressions of pH below 5.0 were found to be lower than those for populations inhabiting lakes that did not experience such acid pulses. The proportional biomass of amphipods in relation to the total littoral zoobenthos community was lower in lakes of low alkalinity than in circumneutral or hardwater lakes. Because production in these amphipod populations is known to depend closely on population abundance, the labour-intensive derivation of production rates yields relatively little information for biomonitoring that cannot be obtained from abundance data alone. PMID:15093505

  2. Biomass and production of amphipods in low alkalinity lakes affected by acid precipitation.

    PubMed

    France, R L

    1996-01-01

    Population biomass and production of the amphipod Hyalella azteca (Saussure) were found to be related to alkalinity (ranging from 0.2 to 58.1 mg liter(-1)) in 10 Canadian Shield lakes in south-central Ontario. Biomass and production of amphipods in the two lakes characterized by spring depressions of pH below 5.0 were found to be lower than those for populations inhabiting lakes that did not experience such acid pulses. The proportional biomass of amphipods in relation to the total littoral zoobenthos community was lower in lakes of low alkalinity than in circumneutral or hardwater lakes. Because production in these amphipod populations is known to depend closely on population abundance, the labour-intensive derivation of production rates yields relatively little information for biomonitoring that cannot be obtained from abundance data alone.

  3. Unusual Nonterrestrial L-proteinogenic Amino Acid excesses in the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Hilts, Robert W.; Herd, D. K.

    2012-01-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography with fluorescence detection and time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approximately 43-59%) of the alpha-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha hydrogen protein amino acid, was found to be nearly racemic (D much approximately L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and 1)- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the L-excesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals. Amplification of a small initial L-enantiomer excess during aqueous alteration on the meteorite parent body could have led to the large L-enrichments observed for aspartic acid and other conglomerate amino acids in Tagish Lake. The detection of non terrestrial L-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life.

  4. Maunder Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 24 May 2002) The Science This image is of a portion of Maunder Crater located at about 49 S and 358 W (2 E). There are a number of interesting features in this image. The lower left portion of the image shows a series of barchan dunes that are traveling from right to left. The sand does not always form dunes as can be seen in the dark and diffuse areas surrounding the dune field. The other interesting item in this image are the gullies that can be seen streaming down from just beneath a number of sharp ridgelines in the upper portion of the image. These gullies were first seen by the MOC camera on the MGS spacecraft and it is though that they formed by groundwater leaking out of the rock layers on the walls of craters. The water runs down the slope and forms the fluvial features seen in the image. Other researchers think that these features could be formed by other fluids, such as CO2. These features are typically seen on south facing slopes in the southern hemisphere, though this image has gullies on north facing slopes as well. The Story Little black squigglies seem to worm their way down the left-hand side of this image. These land features are called barchan (crescent-shaped) dunes. Barchan dunes are found in sandy deserts on Earth, so it's no surprise the Martian wind makes them a common site on the red planet too. They were first named by a Russian scientist named Alexander von Middendorf, who studied the inland desert dunes of Turkistan. The barchan dunes in this image occur in the basin of Maunder crater on Mars, and are traveling from right to left. The sand does not always form dunes, though, as can be seen in the dark areas of scattered sand surrounding the dune field. Look for the streaming gullies that appear just beneath a number of sharp ridgelines in the upper portion of the image. These gullies were first discovered by the Mars Orbital Camera on the Mars Global Surveyor spacecraft. While most crater gullies are found on south

  5. "Hairy blobs:" microbial suspects preserved in modern and ancient extremely acid lake evaporites.

    PubMed

    Benison, Kathleen C; Jagniecki, Elliot A; Edwards, Tina B; Mormile, Melanie R; Storrie-Lombardi, Michael C

    2008-08-01

    "Hairy blobs" are unusual clumps of organic bodies and sulfate crystals that have been found in evaporite minerals grown in acid saline lakes. Here, we document modern hairy blobs in halite and gypsum from 5 modern acid saline lakes in southern Western Australia, and Permian hairy blobs trapped in halite from the mid-Permian Opeche Shale in the subsurface of North Dakota. These are among the first microbial remains described from acid saline lake environments. They give clues about the role of microorganisms in the acidity, geochemistry, and mineralogy of these extreme environments. This study also may add to the inventory of life in extreme environments and help predict possible martian life-forms and the method of preservation. PMID:18498219

  6. "Hairy blobs:" microbial suspects preserved in modern and ancient extremely acid lake evaporites.

    PubMed

    Benison, Kathleen C; Jagniecki, Elliot A; Edwards, Tina B; Mormile, Melanie R; Storrie-Lombardi, Michael C

    2008-08-01

    "Hairy blobs" are unusual clumps of organic bodies and sulfate crystals that have been found in evaporite minerals grown in acid saline lakes. Here, we document modern hairy blobs in halite and gypsum from 5 modern acid saline lakes in southern Western Australia, and Permian hairy blobs trapped in halite from the mid-Permian Opeche Shale in the subsurface of North Dakota. These are among the first microbial remains described from acid saline lake environments. They give clues about the role of microorganisms in the acidity, geochemistry, and mineralogy of these extreme environments. This study also may add to the inventory of life in extreme environments and help predict possible martian life-forms and the method of preservation.

  7. Selective transfer of polyunsaturated fatty acids from phytoplankton to planktivorous fish in large boreal lakes.

    PubMed

    Strandberg, Ursula; Hiltunen, Minna; Jelkänen, Elli; Taipale, Sami J; Kainz, Martin J; Brett, Michael T; Kankaala, Paula

    2015-12-01

    Lake size influences various hydrological parameters, such as water retention time, circulation patterns and thermal stratification that can consequently affect the plankton community composition, benthic-pelagic coupling and the function of aquatic food webs. Although the socio-economical (particularly commercial fisheries) and ecological importance of large lakes has been widely acknowledged, little is known about the availability and trophic transfer of polyunsaturated fatty (PUFA) in large lakes. The objective of this study was to investigate trophic trajectories of PUFA in the pelagic food web (seston, zooplankton, and planktivorous fish) of six large boreal lakes in the Finnish Lake District. Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and α-linolenic acid (ALA) were the most abundant PUFA in pelagic organisms, particularly in the zooplanktivorous fish. Our results show that PUFA from the n-3 family (PUFAn-3), often associated with marine food webs, are also abundant in large lakes. The proportion of DHA increased from ~4±3% in seston to ~32±6% in vendace (Coregonus albula) and smelt (Osmerus eperlanus), whereas ALA showed the opposite trophic transfer pattern with the highest values observed in seston (~11±2%) and the lowest in the opossum shrimp (Mysis relicta) and fish (~2±1%). The dominance of diatoms and cryptophytes at the base of the food web in the study lakes accounted for the high amount of PUFAn-3 in the planktonic consumers. Furthermore, the abundance of copepods in the large lakes explains the effective transfer of DHA to planktivorous fish. The plankton community composition in these lakes supports a fishery resource (vendace) that is very high nutritional quality (in terms of EPA and DHA contents) to humans.

  8. Selective transfer of polyunsaturated fatty acids from phytoplankton to planktivorous fish in large boreal lakes.

    PubMed

    Strandberg, Ursula; Hiltunen, Minna; Jelkänen, Elli; Taipale, Sami J; Kainz, Martin J; Brett, Michael T; Kankaala, Paula

    2015-12-01

    Lake size influences various hydrological parameters, such as water retention time, circulation patterns and thermal stratification that can consequently affect the plankton community composition, benthic-pelagic coupling and the function of aquatic food webs. Although the socio-economical (particularly commercial fisheries) and ecological importance of large lakes has been widely acknowledged, little is known about the availability and trophic transfer of polyunsaturated fatty (PUFA) in large lakes. The objective of this study was to investigate trophic trajectories of PUFA in the pelagic food web (seston, zooplankton, and planktivorous fish) of six large boreal lakes in the Finnish Lake District. Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and α-linolenic acid (ALA) were the most abundant PUFA in pelagic organisms, particularly in the zooplanktivorous fish. Our results show that PUFA from the n-3 family (PUFAn-3), often associated with marine food webs, are also abundant in large lakes. The proportion of DHA increased from ~4±3% in seston to ~32±6% in vendace (Coregonus albula) and smelt (Osmerus eperlanus), whereas ALA showed the opposite trophic transfer pattern with the highest values observed in seston (~11±2%) and the lowest in the opossum shrimp (Mysis relicta) and fish (~2±1%). The dominance of diatoms and cryptophytes at the base of the food web in the study lakes accounted for the high amount of PUFAn-3 in the planktonic consumers. Furthermore, the abundance of copepods in the large lakes explains the effective transfer of DHA to planktivorous fish. The plankton community composition in these lakes supports a fishery resource (vendace) that is very high nutritional quality (in terms of EPA and DHA contents) to humans. PMID:26282609

  9. Gale Crater Mound

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    The eroded, layered deposit in Gale Crater is a mound of material rising 3 km above the crater floor. It has been sculpted by wind and possibly water to produce the dramatic landforms seen today. The origin of the sedimentary material that composes the mound remains a contested issue: was it produced from sedimentation in an ancient crater lake or by airfall onto dry land?

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude -5.1, Longitude 137.5 East (222.5 West). 19 meter/pixel resolution.

  10. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  11. Chemical and biological recovery from acid deposition within the Honnedaga Lake watershed, New York, USA.

    PubMed

    Josephson, Daniel C; Robinson, Jason M; Chiotti, Justin; Jirka, Kurt J; Kraft, Clifford E

    2014-07-01

    Honnedaga Lake in the Adirondack region of New York has sustained a heritage brook trout population despite decades of atmospheric acid deposition. Detrimental impacts from acid deposition were observed from 1920 to 1960 with the sequential loss of acid-sensitive fishes, leaving only brook trout extant in the lake. Open-lake trap net catches of brook trout declined for two decades into the late 1970s, when brook trout were considered extirpated from the lake but persisted in tributary refuges. Amendments to the Clean Air Act in 1990 mandated reductions in sulfate and nitrogen oxide emissions. By 2000, brook trout had re-colonized the lake coincident with reductions in surface-water sulfate, nitrate, and inorganic monomeric aluminum. No changes have been observed in surface-water acid-neutralizing capacity (ANC) or calcium concentration. Observed increases in chlorophyll a and decreases in water clarity reflect an increase in phytoplankton abundance. The zooplankton community exhibits low species richness, with a scarcity of acid-sensitive Daphnia and dominance by acid-tolerant copepods. Trap net surveys indicate that relative abundance of adult brook trout population has significantly increased since the 1970s. Brook trout are absent in 65 % of tributaries that are chronically acidified with ANC of <0 μeq/L and toxic aluminum levels (>2 μmol/L). Given the current conditions, a slow recovery of chemistry and biota is expected in Honnedaga Lake and its tributaries. We are exploring the potential to accelerate the recovery of brook trout abundance in Honnedaga Lake through lime applications to chronically and episodically acidified tributaries. PMID:24671614

  12. Chemical response of lakes in the Adirondack Region of New York to declines in acidic deposition.

    PubMed

    Driscoll, Charles T; Driscoll, Kimberley M; Roy, Karen M; Mitchell, Myron J

    2003-05-15

    Long-term changes in the chemistry of wet deposition and lake water were investigated in the Adirondack Region of New York. Marked decreases in concentrations of SO4(2-) and H+ in wet deposition have occurred at two sites since the late 1970s. These decreases are consistent with long-term declines in emissions of sulfur dioxide (SO2) in the eastern United States. Changes in wet NO3- deposition and nitrogen oxides (NOx) emissions have been minor over the same interval. Virtually all Adirondack Lakes have shown marked decreases in concentrations of SO4(2-), which coincide with decreases in atmospheric S deposition. Concentrations of NO3- have also decreased in several Adirondack lakes. As atmospheric N deposition has not changed over this period, the mechanism contributing to this apparent increase in lake/watershed N retention is not evident. Decreases in concentrations of SO4(2-) + NO3- have resulted in increases in acid-neutralizing capacity (ANC) and pH and resulted in a shift in the speciation of monomeric Al from toxic inorganic species toward less toxic organic forms in some lakes. Nevertheless, many lakes continue to exhibit pH values and concentrations of inorganic monomeric Al that are critical to aquatic biota. Extrapolation of rates of ANC increase suggests that the time frame of chemical recovery of Adirondack Lakes will be several decades if current decreases in acidic deposition are maintained.

  13. Fish population losses from Adirondack Lakes: The role of surface water acidity and acidification

    NASA Astrophysics Data System (ADS)

    Baker, Joan P.; Warren-Hicks, William J.; Gallagher, James; Christensen, Sigurd W.

    1993-04-01

    Changes over time in the species composition of fish communities in Adirondack lakes were assessed to determine (1) the approximate numbers offish populations that have been lost and (2) the degree to which fish population losses may have resulted from surface water acidification and acidic deposition. Information on the present-day status offish communities was obtained by the Adirondack Lakes Survey Corporation, which surveyed 1469 Adirondack lakes in 1984-1987 (53% of the total ponded waters in the Adirondack ecological zone). Two hundred and ninety-five of these lakes had been surveyed in 1929-1934 during the first statewide biological survey; 720 had been surveyed in one or more years prior to 1970. Sixteen to 19% of the lakes with adequate historical data appeared to have lost one or more fish populations as a result of acidification. Brook trout and acid-sensitive minnow species had experienced the most widespread effects. Populations of brook trout and acid-sensitive minnows had been lost apparently as a result of acidification from 11% and 19%, respectively, of the lakes with confirmed historical occurrence of these taxa. By contrast, fish species that tend to occur primarily in lower elevation and larger lakes, such as largemouth and smallmouth bass and brown trout, have experienced little to no documented adverse effects. Lakes that were judged to have lost fish populations as a result of acidification had significantly lower; pH and, in most cases, also had higher estimated concentrations of inorganic aluminum and occurred at higher elevations than did lakes with the fish species still present. No other lake characteristics were consistently associated with fish population losses attributed to acidification. The exact numbers and proportions of fish populations affected could not be determined because of limitations on the quantity and quality of historical data. Lakes for which we had adequate historical data to assess long-term trends in fish

  14. Species diversity of fishes in naturally acidic lakes in New Jersey

    SciTech Connect

    Graham, J.H. )

    1993-11-01

    Fish communities in acidic lakes of New Jersey have fewer species than do those in more alkaline lakes of comparable size. This conclusion is based on a multiple regression analysis of published data on fish communities, area, and pH in 85 lakes. Some interesting patterns emerge, however, when species are partitioned into introduced and native species. As expected, diversity of introduced species declines with increasing acidity. The number of native species in a particular lake, however, is independent of pH (range of 4.1 to 9.1). Although diversity of native species is not influenced by pH, species composition changes. The lack of a significant relationship between species diversity of native species and pH can be attributed to the replacement of acid-intolerant species by tolerant species. The smaller number of introduced species in acidic lakes is attributable to both fewer species stocked and a greater frequency of failure for those that were stocked. Species introduction records for largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus, which are not native to New Jersey, reveal far more failed introduction in acidic waters than in neutral or alkaline waters. 54 refs., 6 figs., 5 tabs.

  15. Assessment of acidity of lakes and precipitation in the Sierra Nevada

    SciTech Connect

    Melack, J.M.

    1983-06-01

    The east central Sierra Nevada received acid precipitation (pH 3.7 to 4.9) during the convective storms interspersed through the dry seasons of 1981 and 1982. In contrast, late autumn, winter and early spring snow (1981-1982) ranged in pH from 5.2 to 6.1 (mean 5.7) and had low ammonium, nitrate and sulfate concentrations. As of 1981 most of the alpine lakes of the Sierra Nevada remain very weakly buffered, bicarbonate lakes that receive a small loading of acid precipitation and a large annual input of snowmelt uncontaminated by strong acids. These lakes contain low concentrations of orthophosphate, nitrate and ammonium and are oligotrophic. The zooplankton communities fall into two major groups, those dominated by large-bodied species in the absence of fish, and those dominated by smaller species where fish are present. If the acidity of the precipitation increases the pH of the lakes will decrease rapidly with adverse biological impacts because the lakes and their basins have extremely low buffer capacity and the biota cannot tolerate acidic water. 65 references, 14 figures, 6 tables.

  16. Changes in acid precipitation-related water chemistry of lakes from southwestern New Brunswick, Canada, 1986-2001.

    PubMed

    Pilgrim, W; Clair, T A; Choate, J; Hughes, R

    2003-01-01

    Between 1986 and 2001, thirty-nine lakes in southwestern New Brunswick in Atlantic Canada were surveyed for acid precipitation-related water quality changes. Most of the study lakes are located on granite bedrock and represent the most acid sensitive lakes in the province. Between 1987 and 1992, hydrogen ion deposition to the lake study area averaged 452 eq ha(-1) yr(-1), compared to 338 eq ha(-1) yr(-1) between 1993 and 2000, a 25% reduction. The lake chemistry data were evaluated by dividing the lakes into four clusters for each survey year based on their acid neutralizing capacity. Twenty percent of the lakes (cluster IV) had an average ANC of 40 microeq L(-1) or greater and maintained an average pH of greater than 6 over the duration of the study period. A pH of 6 or greater is considered a healthy benchmark for maintaining biodiversity. The remaining 31 lakes (clusters I to III) had an average ANC of less than 40 microeq L(-1) and maintained an average pH of less than 6. Other lake chemistry changes included a general decline in lake sulphate and colour over the duration of the survey period, followed by more recent improvements in calcium ion, pH and ANC, and notably higher but declining aluminum levels in lower ANC and pH lakes. Nitrate accounted for 37% of the acid deposition to the study area, however it was not detectable in the lakes. Although acid deposition has declined and these lakes are beginning to show signs of acid recovery, 80% of the study lakes remain acid sensitive having little buffering capacity with low calcium, pH and ANC.

  17. Measurements of slope distances and vertical angles at Mount Baker and Mount Rainier, Washington, Mount Hood and Crater Lake, Oregon, and Mount Shasta and Lassen Peak, California, 1980-1984

    USGS Publications Warehouse

    Chadwick, W.W.

    1985-01-01

    Personnel of the U.S.Geological Survey's Cascades Volcano Observatory established trilateration networks at Mount Baker, Mount Rainier, Mount Hood, Crater Lake, Mount Shasta, and Lassen Peak in 1980-1984. These networks are capable of detecting changes in slope distance of several centimeters or more. The networks were established to provide baseline information on potentially active volcanoes and were designed along guidelines found useful at Mount St. Helens. Periodic reoccupation of the networks is planned as part of the overall monitoring program of Cascades volcanoes. Methodology, slope distance and vertical angle data, maps of the networks, and benchmark descriptions are presented in this report. Written benchmark descriptions are augmented by photographs, which we have found by experience to very useful in relocating the marks. All repeat measurements at the six volcanoes are probably within measurement error.

  18. Generation of Acid Mine Lakes Associated with Abandoned Coal Mines in Northwest Turkey.

    PubMed

    Sanliyuksel Yucel, Deniz; Balci, Nurgul; Baba, Alper

    2016-05-01

    A total of five acid mine lakes (AMLs) located in northwest Turkey were investigated using combined isotope, molecular, and geochemical techniques to identify geochemical processes controlling and promoting acid formation. All of the investigated lakes showed typical characteristics of an AML with low pH (2.59-3.79) and high electrical conductivity values (1040-6430 μS/cm), in addition to high sulfate (594-5370 mg/l) and metal (aluminum [Al], iron [Fe], manganese [Mn], nickel [Ni], and zinc [Zn]) concentrations. Geochemical and isotope results showed that the acid-generation mechanism and source of sulfate in the lakes can change and depends on the age of the lakes. In the relatively older lakes (AMLs 1 through 3), biogeochemical Fe cycles seem to be the dominant process controlling metal concentration and pH of the water unlike in the younger lakes (AMLs 4 and 5). Bacterial species determined in an older lake (AML 2) indicate that biological oxidation and reduction of Fe and S are the dominant processes in the lakes. Furthermore, O and S isotopes of sulfate indicate that sulfate in the older mine lakes may be a product of much more complex oxidation/dissolution reactions. However, the major source of sulfate in the younger mine lakes is in situ pyrite oxidation catalyzed by Fe(III) produced by way of oxidation of Fe(II). Consistent with this, insignificant fractionation between δ(34) [Formula: see text] and δ(34) [Formula: see text] values indicated that the oxidation of pyrite, along with dissolution and precipitation reactions of Fe(III) minerals, is the main reason for acid formation in the region. Overall, the results showed that acid generation during early stage formation of an AML associated with pyrite-rich mine waste is primarily controlled by the oxidation of pyrite with Fe cycles becoming the dominant processes regulating pH and metal cycles in the later stages of mine lake development. PMID:26987541

  19. Polymethylene-interrupted fatty acids: Biomarkers for native and exotic mussels in the Laurentian Great Lakes

    USGS Publications Warehouse

    Mezek, Tadej; Sverko, Ed; Ruddy, Martina D.; Zaruk, Donna; Capretta, Alfredo; Hebert, Craig E.; Fisk, Aaron T.; McGoldrick, Daryl J.; Newton, Teresa J.; Sutton, Trent M.; Koops, Marten A.; Muir, Andrew M.; Johnson, Timothy B.; Ebener, Mark P.; Arts, Michael T.

    2011-01-01

    Freshwater organisms synthesize a wide variety of fatty acids (FAs); however, the ability to synthesize and/or subsequently modify a particular FA is not universal, making it possible to use certain FAs as biomarkers. Herein we document the occurrence of unusual FAs (polymethylene-interrupted fatty acids; PMI-FAs) in select freshwater organisms in the Laurentian Great Lakes. We did not detect PMI-FAs in: (a) natural seston from Lake Erie and Hamilton Harbor (Lake Ontario), (b) various species of laboratory-cultured algae including a green alga (Scenedesmus obliquus), two cyanobacteria (Aphanizomenon flos-aquae and Synechococystis sp.), two diatoms (Asterionella formosa, Diatoma elongatum) and a chrysophyte (Dinobryon cylindricum) or, (c) zooplankton (Daphnia spp., calanoid or cyclopoid copepods) from Lake Ontario, suggesting that PMI-FAs are not substantively incorporated into consumers at the phytoplankton–zooplankton interface. However, these unusual FAs comprised 4-6% of total fatty acids (on a dry tissue weight basis) of native fat mucket (Lampsilis siliquoidea) and plain pocketbook (L. cardium) mussels and in invasive zebra (Dreissena polymorpha) and quagga (D. bugensis) mussels. We were able to clearly partition Great Lakes' mussels into three separate groups (zebra, quagga, and native mussels) based solely on their PMI-FA profiles. We also provide evidence for the trophic transfer of PMI-FAs from mussels to various fishes in Lakes Ontario and Michigan, further underlining the potential usefulness of PMI-FAs for tracking the dietary contribution of mollusks in food web and contaminant-fate studies.

  20. Variation in Lake Michigan alewife (Alosa pseudoharengus) thiaminase and fatty acids composition

    USGS Publications Warehouse

    Honeyfield, D.C.; Tillitt, D.E.; Fitzsimons, J.D.; Brown, S.B.

    2010-01-01

    Thiaminase activity of alewife (Alosa pseudoharengus) is variable across Lake Michigan, yet factors that contribute to the variability in alewife thiaminase activity are unknown. The fatty acid content of Lake Michigan alewife has not been previously reported. Analysis of 53 Lake Michigan alewives found a positive correlation between thiaminase activity and the following fatty acid: C22:ln9, sum of omega-6 fatty acids (Sw6), and sum of the polyunsaturated fatty acids. Thiaminase activity was negatively correlated with C15:0, C16:0, C17:0, C18:0, C20:0, C22:0, C24:0, C18:ln9t, C20:3n3, C22:2, and the sum of all saturated fatty acids (SAFA). Multi-variant regression analysis resulted in three variables (C18:ln9t, Sw6, SAFA) that explained 71% (R2=0.71, P<0.0001) of the variation in thiaminase activity. Because the fatty acid content of an organism is related is food source, diet may be an important factor modulating alewife thiaminase activity. These data suggest there is an association between fatty acids and thiaminase activity in Lake Michigan alewife.

  1. Late Holocene hydrous mafic magmatism at the Paint Pot Crater and Callahan flows, Medicine Lake Volcano, N. California and the influence of H2O in the generation of silicic magmas

    USGS Publications Warehouse

    Kinzler, R.J.; Donnelly-Nolan, J. M.; Grove, T.L.

    2000-01-01

    This paper characterizes late Holocene basalts and basaltic andesites at Medicine Lake volcano that contain high pre-eruptive H2O contents inherited from a subduction related hydrous component in the mantle. The basaltic andesite of Paint Pot Crater and the compositionally zoned basaltic to andesitic lavas of the Callahan flow erupted approximately 1000 14C years Before Present (14C years B.P.). Petrologic, geochemical and isotopic evidence indicates that this late Holocene mafic magmatism was characterized by H2O contents of 3 to 6 wt% H2O and elevated abundances of large ion lithophile elements (LILE). These hydrous mafic inputs contrast with the preceding episodes of mafic magmatism (from 10,600 to ~3000 14C years B.P.) that was characterized by the eruption of primitive high alumina olivine tholeiite (HAOT) with low H2O (< 0.2 wt%), lower LILE abundance and different isotopic characteristics. Thus, the mantle-derived inputs into the Medicine Lake system have not always been low H2O, primitive HAOT, but have alternated between HAOT and hydrous subduction related, calc-alkaline basalt. This influx of hydrous mafic magma coincides temporally and spatially with rhyolite eruption at Glass Mountain and Little Glass Mountain. The rhyolites contain quenched magmatic inclusions similar in character to the mafic lavas at Callahan and Paint Pot Crater. The influence of H2O on fractional crystallization of hydrous mafic magma and melting of pre-existing granite crust beneath the volcano combined to produce the rhyolite. Fractionation under hydrous conditions at upper crustal pressures leads to the early crystallization of Fe-Mg silicates and the suppression of plagioclase as an early crystallizing phase. In addition, H2O lowers the saturation temperature of Fe and Mg silicates, and brings the temperature of oxide crystallization closer to the liquidus. These combined effects generate SiO2-enrichment that leads to rhyodacitic differentiated lavas. In contrast, low H2O HAOT

  2. A detailed geologic characterization of Eberswalde crater, Mars

    NASA Astrophysics Data System (ADS)

    Rice, M. S.; BellI, J. F., III; Gupta, S.; Warner, N. H.; Goddard, K.; Anderson, R. B.

    Background: Eberswalde crater, selected as one of four finalist landing sites for the Mars Science Laboratory mission, is best known for the spectacularly preserved, inverted, fan-shaped deposit along its western margin. This feature has been interpreted as a lacustrine delta, although the timing and duration of an Eberswalde crater lake is poorly understood. The aim of this study is to place more broadly observed fluvio-lacustrine activity throughout the crater's floor within the larger context of Eberswalde's geologic history, and to infer the sequence of deposition and erosion of the observed stratigraphic and geomorphic units. Method: We have identified and mapped stratigraphic and geomorphic units within all of Eberswalde crater using orbital imagery from the HiRISE, MOC and CTX cameras, and we have calculated crater statistics to infer the relative ages of crater floor materials. Using topographic datasets derived from HiRISE, CTX and MOLA, we determine the unit associations, successions, and geometries and develop a model for the depositional and erosional history within the crater. Conclusion: We have produced maps of ten stratigraphic and seven geomorphic units identified within Eberswalde crater. Our observations of the stratigraphy, geomorphology, topography and crater densities imply a complex relationship between deposition and exhumation within Eberswalde crater, and we infer the following sequence of major events: (1) Eberswalde crater forms in the Noachian (> 3.6 Ga); (2) Holden crater forms southwest of Eberswalde crater in the late Noachian to Early Hesperian, and its associated ejecta blanket covers the floor of Eberswalde crater and heavily modifies the southern rim; (3) Extensive faulting from regional stresses creates the first-order topography within the crater, and vein-like features form in some units from fracturing, fluid circulation, and cementation; (4) Valley features are carved in the crater walls as water flows into the crater

  3. Chemical and biological status of lakes and streams in the upper midwest: assessment of acidic deposition effects

    USGS Publications Warehouse

    Wiener, J.G.; Eilers, J.M.

    1987-01-01

    Many lakes in three areas in the Upper Midwest - northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan - have low acid neutralizing capacity (ANC) and may be susceptible to change by acidic deposition. Northcentral Wisconsin and the Upper Peninsula of Michigan together contain about 150-300 acidic lakes (ANC ≤ 0), whereas none have been found in Minnesota. These acidic lakes are precipitation-dominated, Clearwater seepage lakes having small surface area, shallow depth, and low concentrations of dissolved organic carbon. The spatial distribution of these acidic lakes parallels a west to east gradient of increasing sulfate and hydrogen ion deposition. Several of these acidic lakes exhibit chemical characteristics and biological changes consistent with those observed elsewhere in waters reported to be acidified by acidic deposition. However, an hypothesis of recent lake acidification is not supported by analyses of either historical chemical data or diatom remains in lake sediments, and natural sources of acidity and alternative ecological processes have not been conclusively eliminated as causative factors. Streams in this three-state region have high ANC and appear to be insensitive to acidic deposition. The species richness and composition of lacustrine fish communities in the region are partly related to pH and associated chemical factors. Sport fishes considered acid-sensitive and of primary concern with regard to acidification include walleye, smallmouth bass, and black crappie. The fishery in at least one lake, Morgan Lake in Wisconsin (pH 4.6), may have declined because of acidification. Given the general lack of quantitative fishery data for acidic Wisconsin and Michigan lakes, however, more general conclusions concerning impacts or the absence of impacts of acidification on the region's fishery resources are not possible.

  4. Crater chains on Mercury

    NASA Astrophysics Data System (ADS)

    Shevchenko, V.; Skobeleva, T.

    After discovery of disruption comet Shoemaker-Levy 9 into fragment train before it's collision with Jupiter there was proposed that linear crater chains on the large satellites of Jupiter and on the Moon are impact scars of past tidally disrupted comets.It's known that radar images have revealed the possible presence of water ice deposits in polar regions of Mercury. Impacts by a few large comets seem to provide the best explanation for both the amount and cleanliness of the ice deposits on Mercury because they have a larger volatile content that others external sources, for example, asteroid. A number of crater chains on the surface of Mercury are most likely the impact tracks of "fragment trains" of comets tidally disrupted by Sun or by Mercury and are not secondary craters. Mariner 10 image set (the three Mariner 10 flybys in 1974-1975) was used to recognize the crater chains these did not associate with secondary crater ejecta from observed impact structures. As example, it can be shown such crater chain located near crater Imhotep and crater Ibsen (The Kuiper Quadrangle of Mercury). Resolution of the Mariner 10 image is about 0.54 km/pixel. The crater chain is about 50 km long. It was found a similar crater chain inside large crater Sophocles (The Tolstoj Quadrangle of Mercury). The image resolution is about 1.46 km/pixel. The chain about 50 km long is located in northen part of the crater. Image resolution limits possibility to examine the form of craters strongly. It seems the craters in chains have roughly flat floor and smooth form. Most chain craters are approximately circular. It was examined many images from the Mariner 10 set and there were identified a total 15 crater chains and were unable to link any of these directly to any specific large crater associated with ejecta deposits. Chain craters are remarkably aligned. All distinguished crater chains are superposed on preexisting formations. A total of 127 craters were identified in the 15 recognized

  5. Integrated Lake-Watershed Acidification Study (ILWAS): contributions to the international conference on the ecological impact of acid precipitation

    SciTech Connect

    Not Available

    1981-05-01

    The Integrated Lake-Watershed Acidification Study (ILWAS) was initiated to study and detail lake acidification processes for three lake watershed basins in the Adirondack Park region of New York. The three basins (Woods, Sagamore, and Panther), receive similar amounts of acid deposition yet observable pH values for the lakes are very dissimilar indicating unequal acid neutralizing capacities among the watersheds. This volume contains a compilation of seven papers. Relevant topics include: a characterization of the geology, hydrology, limnology and vegetation of the three study sites, an analysis of acid precipitation quality and quantity, the effects of vegetative canopy, the effects of snowmelt, the effects of winter lake stratification, comparison of heavy metal transport, examination of acidic sources other than direct precipitation, assessment of lake acidification during spring thaw and integration of all acidification components with a mathematical model.

  6. Pollack Crater's White Rock

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image of White Rock in Pollack crater was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on February 3, 2007 at 1750 UTC (12:50 p.m. EST), near 8 degrees south latitude, 25 degrees east longitude. The CRISM image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 40 meters (132 feet) across. The region covered is roughly 20 kilometers (12 miles) long and 10 kilometers (6 miles) wide at its narrowest point.

    First imaged by the Mariner 9 spacecraft in 1972, the enigmatic group of wind-eroded ridges known as White Rock has been the subject of many subsequent investigations. White Rock is located on the floor of Pollack Crater in the Sinus Sabaeus region of Mars. It measures some 15 by 18 kilometers (9 by 11 miles) and was named for its light-colored appearance. In contrast-enhanced images, the feature's higher albedo or reflectivity compared with the darker material on the floor of the crater makes it appear white. In reality, White Rock has a dull, reddish color more akin to Martian dust. This higher albedo as well as its location in a topographic low suggested to some researchers that White Rock may be an eroded remnant of an ancient lake deposit. As water in a desert lake on Earth evaporates, it leaves behind white-colored salts that it leached or dissolved out of the surrounding terrain. These salt deposits may include carbonates, sulfates, and chlorides.

    In 2001, the Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor measured White Rock and found no obvious signature of carbonates or sulfates, or any other indication that White Rock holds evaporite minerals. Instead, it found Martian dust.

    CRISM's challenge was to obtain greater detail of White Rock's mineralogical composition and how it formed. The instrument operates at a different wavelength range than TES, giving it greater sensitivity to carbonate, sulfate and phyllosilicate (clay-like) minerals. It also

  7. Holden Crater/Uzboi Valles

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 17 April 2002) The Science This image, located near 27.0S and 35.5W (324.5E), displays the intersection of Holden Crater with Uzboi Valles. This region of Mars contains a number of features that could be related to liquid water on the surface in the Martian past. Holden Crater contains finely layered sedimentary units that have been subsequently dissected. The hummucky terrain in the bottom half of the image is the remnants of this terrain, though the fine layers are not visible in this image at this resolution. The sedimentary units could have formed through deposition of material in a lacustrine type environment. Alternately, these layers could also be volcanic ash deposits. Uzboi Valles, which enters the crater from the southwest, is a catastrophic outflow channel that formed in the Martian past. The streamlined nature of the topographic features at the intersection of the crater with Uzboi Valles record the erosional pattern of flowing liquid water on the surface of Mars during the episodic outflow event. The Story Mars doesn't have a shortage of rugged terrain, and this area is no exception. While things look pretty quiet now, this cratered region was once the scene of some tremendous action. Long ago in Martian history, an incoming meteoroid probably smashed into the planet and produced a giant impact crater named Holden Crater, which stretches 88 miles across the Martian surface. The history of the area around Holden Crater doesn?t stop there. At some point, a catastrophic flood burst forth on the surface, forming an impressive outflow channel called Uzboi Valles. No one knows exactly how that happened, or whether the water might even have rushed into Holden Crater at some point, forming a long-ago lake. What we do know is that there is a lot of sedimentary material that could have formed in two hypothesized ways: in an ancient lake environment or as volcanic-ash deposits. Scientists are searching for the answers by studying the region where Uzboi

  8. Evaluating long-term trends in littoral benthic macroinvertebrate communities of lakes recovering from acid deposition.

    PubMed

    Lento, Jennifer; Dillon, Peter J; Somers, Keith M

    2012-12-01

    The Mann-Kendall test has been proposed as a nonparametric method to evaluate trends in long-term water quality datasets with missing values, serial correlation, and non-normality. However, this test has rarely been used to evaluate long-term trends in biological data. In this study, we used the Mann-Kendall test to evaluate trends in 15 years of data on benthic macroinvertebrate communities from 17 Precambrian Shield lakes. We also used the van Belle and Hughes test of trend homogeneity to assess whether common among-lake temporal trends existed. We assumed that evidence of a common regional trend among lakes would support the hypothesis of long-term biological recovery from past acidification. We found decreasing proportions of Chironomidae and increasing proportions of Ephemeroptera, Plecoptera, and Trichoptera (EPT) in both single-lake and multi-lake trend analysis. Moreover, six of the nine lakes with significant trends in more than one benthos metric displayed a significant decrease in Chironomidae and increase in EPT concurrently, indicating a shift towards more acid-sensitive taxa. Weak trends in several of the biological metrics indicated that recovery in these lakes has been impeded. Results of this study indicate that the Mann-Kendall and van Belle and Hughes trend tests are useful statistical tools to evaluate long-term patterns in biological data.

  9. Evaluating long-term trends in littoral benthic macroinvertebrate communities of lakes recovering from acid deposition.

    PubMed

    Lento, Jennifer; Dillon, Peter J; Somers, Keith M

    2012-12-01

    The Mann-Kendall test has been proposed as a nonparametric method to evaluate trends in long-term water quality datasets with missing values, serial correlation, and non-normality. However, this test has rarely been used to evaluate long-term trends in biological data. In this study, we used the Mann-Kendall test to evaluate trends in 15 years of data on benthic macroinvertebrate communities from 17 Precambrian Shield lakes. We also used the van Belle and Hughes test of trend homogeneity to assess whether common among-lake temporal trends existed. We assumed that evidence of a common regional trend among lakes would support the hypothesis of long-term biological recovery from past acidification. We found decreasing proportions of Chironomidae and increasing proportions of Ephemeroptera, Plecoptera, and Trichoptera (EPT) in both single-lake and multi-lake trend analysis. Moreover, six of the nine lakes with significant trends in more than one benthos metric displayed a significant decrease in Chironomidae and increase in EPT concurrently, indicating a shift towards more acid-sensitive taxa. Weak trends in several of the biological metrics indicated that recovery in these lakes has been impeded. Results of this study indicate that the Mann-Kendall and van Belle and Hughes trend tests are useful statistical tools to evaluate long-term patterns in biological data. PMID:22193633

  10. Estimation of critical loads of acidity for lakes in northeastern United States and eastern Canada.

    PubMed

    Dupont, J; Clair, T A; Gagnon, C; Jeffries, D S; Kahl, J S; Nelson, S J; Peckenham, J M

    2005-10-01

    The New England Governors and Eastern Canadian Premiers (NEG/ECP) adopted the Acid Rain Action Plan in June 1998, and issued a series of action items to support its work toward a reduction of sulfur dioxide (SO(2)) and nitrogen oxide (NO(x)) emissions in northeastern North America. One of these action items was the preparation of an updated critical load map using data from lakes in the NEG/ECP area. Critical load maps provide a more complete index of the surface water sensitivity to acidification. Combined sulfur and nitrogen critical loads and deposition exceedances were computed using Henriksen's Steady-State Water Chemistry (SSWC) model. Results show that 28% of all 2053 lakes studied have a critical load of 20 kg/ha/year or less, making them vulnerable to acid deposition. Emission reductions, and more specifically SO(2) emission reductions have proven beneficial because critical loads were exceeded in 2002 for 12.3% of all studied lakes. Those lakes are located in the more sensitive areas where geology is carbonate-poor. Of these lakes, 2.9% will never recover even with a complete removal of SO(4) deposition. Recovery from acidification for the remaining 9.4% of the lakes will require additional emission SO(2) reductions.

  11. Stable carbon and nitrogen isotopes and amino acids in Holocene sediments of Lake Lonar, central India

    NASA Astrophysics Data System (ADS)

    Menzel, Philip; Gaye, Birgit; Wiesner, Martin; Basavaiah, Nathani; Prasad, Sushma; Stebich, Martina; Anoop, Ambili; Riedel, Nils

    2013-04-01

    Investigations on surface sediments and a sediment core from Lake Lonar in central India were carried out within the framework of the HIMPAC (Himalaya: Modern and Past Climate) programme. The aim was to understand recent productivity, sedimentation, and degradation processes and to reconstruct variations in Holocene lake conditions on the basis of biogeochemical analysis on a 10 m long sediment core retrieved from the centre of Lake Lonar. Located in India's core monsoon zone, Lake Lonar offers valuable information about the climate development of the whole region. The lake is situated at the floor of a meteorite impact structure on the Deccan plateau basalt. The modern lake is characterised by brackish water, high alkalinity, severe eutrophication, and bottom water anoxia. The lake is about 6 m deep and fed by rainfall during the SW monsoon season and three perennial streams. Since no out-flowing stream is present and no seepage loss occurs, the lake level is highly sensitive to the balance of precipitation and evaporation. Here we present C/N, carbon and nitrogen isotope, and amino acid data of bulk organic matter from modern lake and Holocene core sediments. Modern conditions are mainly related to human activity which started to have persistent influence on the biological and chemical lake properties at ~1200 cal a BP. The distribution of δ13C in the modern sediments is driven by the ratio between terrestrial and aquatic organic matter, while δ15N seems to be influenced by redox conditions at the sediment-water-interface with elevated values at shallow oxic stations. Differences in the amino acid assemblages of oxic and anoxic surface sediment samples were used to calculate an Ox/Anox ratio indicating the redox conditions during organic matter degradation. The onset of the monsoon reconstructed from the sediment core occurred at ca. 11450 cal a BP. The early Holocene core sediments are characterised by low sedimentation rate, low aquatic productivity, and

  12. Holden Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Ripple bedforms fill large fractures near the southern rim of Holden Crater.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  13. Becquerel Crater

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03676 Linear Clouds

    This interesting deposit is located on the floor of Becquerel Crater.

    Image information: VIS instrument. Latitude 21.3N, Longitude 352.2E. 18 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. Crater Rim

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    The late afternoon sun casts a shadow over a 700 meter-high rim of Huygens Crater.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude -15.2, Longitude 51.6 East (308.4 West). 19 meter/pixel resolution.

  15. Impact Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    The irregularly shaped rim of this bowl shaped impact crater is most likely due to erosion and the subsequent infilling of sediment.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. Rampart Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Rampart crater in Utopia Planitia west of the Viking 2 landing site.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. Analysis of southeastern Canada lake-water chemistry data in relation to acidic deposition

    SciTech Connect

    Olson, R.J.; Cook, R.B.; Ross-Todd, B.M.; Beauchamp, J.J.

    1990-05-01

    Lake-water chemistry data were obtained for lakes in southeastern Canada to study relationships between atmospheric deposition and acid-base chemistry as part of the National Acid Precipitation Assessment Program State of Science and Technology reports. Quality assurance checks were made to ensure that the data used were of sufficient quality and were comparable to data from the United States. Ninety-eight percent of the 8506 sampled lakes had pH, ANC, and SO{sub 4}{sup 2 {minus}} data and were used in our analyses. Of these, we created a subset of 4017 lakes having data for more variable (Ca{sup 2+}, Mg{sup 2+}, Na{sup +}, K{sup +}, DOC, and conductivity) to analyze potential sources of lake-water acidity. The objectives of this work were to determine the geographical extent and number of potentially affected systems and to infer causes of acidification based on ion ratios. 35 refs., 28 figs., 12 tabs.

  18. Spatial characterization of acid rain stress in Canadian Shield Lakes

    NASA Technical Reports Server (NTRS)

    Tanis, Fred J.

    1987-01-01

    An analysis was performed to interpret the spatial aspects of lake acidification. Three types of relationships were investigated based upon the August to May seasonal scene pairing. In the first type of analysis ANOVA was used to examine the mean Thematic Mapper band one count by ecophysical strata. The primary difference in the two ecophysical strata is the soil type and depth over the underlying bedrock. Examination of the August to May difference values for TM band one produced similar results. Group A and B strata were the same as above. The third type of analysis examined the relationship between values of the August to May difference from polygons which have similar ecophysical properties with the exception of sulfate deposition. For this case lakes were selected from units with sandy soils over granitic rock types and the sulfate deposition was 1.5 or 2.5 g/sq m/yr.

  19. Impacts on water quality and biota from natural acid rock drainage in Colorado's Lake Creek watershed

    USGS Publications Warehouse

    Bird, D.A.; Sares, Matthew A.; Policky, Greg A.; Schmidt, Travis S.; Church, Stanley E.

    2006-01-01

    Colorado's Lake Creek watershed hosts natural acid rock drainage that significantly impacts surface water, streambed sediment, and aquatic life. The source of the ARD is a group of iron-rich springs that emerge from intensely hydrothermally altered, unexploited, low-grade porphyry copper mineralization in the Grizzly Peak Caldera. Source water chemistry includes pH of 2.5 and dissolved metal concentrations of up to 277 mg/L aluminum, 498 mg/L iron, and 10 mg/L copper. From the hydrothermally altered area downstream for 27 kilometers to Twin Lakes Reservoir, metal concentrations in streambed sediment are elevated and the watershed experiences locally severe adverse impacts to aquatic life due to the acidic, metal-laden water. The water and sediment quality of Twin Lakes Reservoir is sufficiently improved that the reservoir supports a trout fishery, and remnants of upstream ARD are negligible.

  20. Incipient sympatric speciation in Midas cichlid fish from the youngest and one of the smallest crater lakes in Nicaragua due to differential use of the benthic and limnetic habitats?

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Torres-Dowdall, Julian; Meyer, Axel

    2016-08-01

    Understanding how speciation can occur without geographic isolation remains a central objective in evolutionary biology. Generally, some form of disruptive selection and assortative mating are necessary for sympatric speciation to occur. Disruptive selection can arise from intraspecific competition for resources. If this competition leads to the differential use of habitats and variation in relevant traits is genetically determined, then assortative mating can be an automatic consequence (i.e., habitat isolation). In this study, we caught Midas cichlid fish from the limnetic (middle of the lake) and benthic (shore) habitats of Crater Lake Asososca Managua to test whether some of the necessary conditions for sympatric speciation due to intraspecific competition and habitat isolation are given. Lake As. Managua is very small (<900 m in diameter), extremely young (maximally 1245 years of age), and completely isolated. It is inhabited by, probably, only a single endemic species of Midas cichlids, Amphilophus tolteca. We found that fish from the limnetic habitat were more elongated than fish collected from the benthic habitat, as would be predicted from ecomorphological considerations. Stable isotope analyses confirmed that the former also exhibit a more limnetic lifestyle than the latter. Furthermore, split-brood design experiments in the laboratory suggest that phenotypic plasticity is unlikely to explain much of the observed differences in body elongation that we observed in the field. Yet, neutral markers (microsatellites) did not reveal any genetic clustering in the population. Interestingly, demographic inferences based on RAD-seq data suggest that the apparent lack of genetic differentiation at neutral markers could simply be due to a lack of time, as intraspecific competition may only have begun a few hundred generations ago. PMID:27551387

  1. Incipient sympatric speciation in Midas cichlid fish from the youngest and one of the smallest crater lakes in Nicaragua due to differential use of the benthic and limnetic habitats?

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Torres-Dowdall, Julian; Meyer, Axel

    2016-08-01

    Understanding how speciation can occur without geographic isolation remains a central objective in evolutionary biology. Generally, some form of disruptive selection and assortative mating are necessary for sympatric speciation to occur. Disruptive selection can arise from intraspecific competition for resources. If this competition leads to the differential use of habitats and variation in relevant traits is genetically determined, then assortative mating can be an automatic consequence (i.e., habitat isolation). In this study, we caught Midas cichlid fish from the limnetic (middle of the lake) and benthic (shore) habitats of Crater Lake Asososca Managua to test whether some of the necessary conditions for sympatric speciation due to intraspecific competition and habitat isolation are given. Lake As. Managua is very small (<900 m in diameter), extremely young (maximally 1245 years of age), and completely isolated. It is inhabited by, probably, only a single endemic species of Midas cichlids, Amphilophus tolteca. We found that fish from the limnetic habitat were more elongated than fish collected from the benthic habitat, as would be predicted from ecomorphological considerations. Stable isotope analyses confirmed that the former also exhibit a more limnetic lifestyle than the latter. Furthermore, split-brood design experiments in the laboratory suggest that phenotypic plasticity is unlikely to explain much of the observed differences in body elongation that we observed in the field. Yet, neutral markers (microsatellites) did not reveal any genetic clustering in the population. Interestingly, demographic inferences based on RAD-seq data suggest that the apparent lack of genetic differentiation at neutral markers could simply be due to a lack of time, as intraspecific competition may only have begun a few hundred generations ago.

  2. Huygens Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 15 July 2003

    The floor of the 450 km diameter crater named after Dutch astronomer Christian Huygens (1629-1695) shows an unusual texture. Smooth-topped mesas are scattered across a more rugged surface. The mesas are testament to a former smooth layer of material that is in the process of eroding away.

    Image information: VIS instrument. Latitude -16.2, Longitude 54.5 East (305.5 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. Martian Meteor Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    20 February 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a fairly young meteor impact crater on Mars that is about the same size ( 1 kilometer; 0.62 miles) as the famous Meteor Crater in northern Arizona, U.S.A. Like the Arizona crater, boulders of ejected bedrock can be seen on the crater's ejecta blanket and in the crater itself. This crater is located in the Aethiopis region of Mars near 4.7oN, 224.1oW. Sunlight illuminates the scene from the lower left.

  4. Response of DOC in acid-sensitive Maine lakes to decreasing sulfur deposition (1993 - 2009)

    EPA Science Inventory

    In response to the Clean Air Act Amendments of 1990, sulfur deposition has decreased across the northeastern United States. As a result, sulfate concentrations in lakes and streams have also decreased and many surface waters have become less acidic. Over the same time period, th...

  5. Hydrothermal Occurrences in Gusev Crater

    NASA Astrophysics Data System (ADS)

    Ruff, S. W.; Farmer, J. D.; Milliken, R.; Mills, V. W.; Shock, E.

    2011-12-01

    Exploration of the Gusev crater landing site by the Spirit rover has revealed for the first time, in situ evidence of hydrothermal activity on Mars. Most compelling are eroded outcrops of opaline silica found adjacent to "Home Plate" [1], an eroded stack of volcaniclastic deposits stratigraphically overlain by a vesicular basalt unit [2]. Recent work [3] demonstrates that the silica outcrops occur in a stratiform unit that possibly surrounds Home Plate. The outcrops are dominated by opal-A with no evidence for diagenesis to other silica phases. No other hydrous or alteration phases have been identified within the outcrops; most notable is a lack of sulfur phases. The outcrops have porous and in some cases, brecciated microtextures. Taken together, these observations support the interpretation that the opaline silica outcrops were produced in a hot spring or perhaps geyser environment. In this context, they are silica sinter deposits precipitated from silica-rich hydrothermal fluids, possibly related to the volcanism that produced the Home Plate volcanic rocks. On Earth, debris aprons in which sinter is brecciated, reworked, and cemented, are common features of hot springs and geysers and are good analogs for the Martian deposits. An alternative hypothesis is that the silica resulted from acid-sulfate leaching of precursor rocks by fumarolic steam condensates. But stratigraphic, textural, and chemical observations tend to diminish this possibility [3]. We are conducting extensive laboratory and field investigations of silica from both hot spring/geyser and fumarole environments to understand the full range of mineralogical, chemical, textural, and morphological variations that accompany its production, in order to shed more light on the Home Plate occurrence. The recent discovery of abundant Mg-Fe carbonate (16-34 wt%) in outcrops named Comanche provides possible evidence for additional hydrothermal activity in Gusev [4]. However, the carbonate is hosted by olivine

  6. Recolonization of acid-damaged lakes by the benthic invertebrates Stenacron interpunctatum, Stenonema femoratum and Hyalella azteca.

    PubMed

    Snucins, Ed

    2003-04-01

    The recolonization of acid-damaged lakes in Killarney Park, Canada is described for 3 species of benthic invertebrates; 2 mayflies (Stenonema femoratum, Stenacron interpunctatum) and an amphipod (Hyalella azteca). Synoptic surveys of 119 lakes for amphipods and 77 lakes for mayflies were conducted between 1995 and 1997 and defined pH thresholds of 5.6 for S. femoratum and H. azteca and pH 5.3 for S. interpunctatum. In an intensive study of 2 acid-damaged lakes and 2 reference lakes from 1997 to 2002, reestablishment of S. interpunctatum, S. femoratum and H. azteca occurred, when timing of the events could be estimated, less than 4-8 years after pH thresholds for specific taxa were reached. Dispersal of S. interpunctatum to all habitat patches within a lake was completed 3 years after recolonization was detected in the smallest lake (11 ha). It is anticipated that dispersal throughout the largest lake (189 ha) will take much longer. The time lag from estimated pH recovery to reestablishment and subsequent dispersal of mayflies to all suitable habitats within a lake was as much as 11 to 22+ years. The density of S. interpunctatum increased in the recovering lakes to levels higher than in reference lakes, but stable endpoints have not yet been reached during 6 years of monitoring.

  7. Decreased acid deposition and the chemical recovery of Killarney, Ontario, lakes.

    PubMed

    Keller, Wendel; Heneberry, Jocelyne H; Dixit, Sushil S

    2003-04-01

    Lakes in Killarney Park near Sudbury, Ontario, Canada, have shown dramatic water quality changes including general increases in pH and alkalinity, and decreases in SO4(2-), base cations and metals. While some lakes have recovered to pH > 6.0, many are still highly acidic despite decades of improvement. Very high historical S deposition related to emissions from the Sudbury metal smelters dominated the acidification process in this region. However, since the implementation of substantial S emission controls (90%) at the smelters, the Sudbury emissions are no longer the major source of S deposition in the Sudbury area. Wet deposition of SO4(2-) and SO4(2-) concentrations in lakewaters at Killarney now approach values in the Dorset, Ontario, area, about 200 km from Sudbury. This suggests that the S deposition to the Killarney area is now primarily from long-range transport, not from local sources. Studies of Killarney lakes are revealing the complex nature of the chemical recovery process. As lake acidity decreases, other changes including decreased Ca2+ concentrations, increased transparency, and altered thermal regimes may potentially affect some of these ecosystems. It is clear that continuing assessments of the recovery of Killarney lakes, within a multiple-stressor framework, are needed.

  8. Comments on cladocerans of crater lakes of the Nevado de Toluca Volcano (Central Mexico), with the description of a new species, Alona manueli sp. nov.

    PubMed

    Sinev, Artem Y; Zawisza, Edyta

    2013-01-01

    Cladoceran communities of two lakes of Nevado de Toluca Volcano, Central Mexico, were studied. A new species of Aloninae, Alona manueli sp. nov., is described. It was previously confused with Palearctic Alona intermedia Sars, 1862, but clearly differs from it in the morphology of postabdomen, head shield and head pores, and thoracic limbs. Position of Alona manueli sp. nov. within the genus is unclear, it did not belong to any species-group within Alona s. lato. Other species recorded in the studied lakes are Alona ossiani Sinev, 1998, Alonella pulchella Herrick, 1884, Chydorus belonging to sphaericus-group, Eurycercus longirostris Hann, 1982 and Pleuroxus cf. denticulatus Birge, 1879.

  9. Comments on cladocerans of crater lakes of the Nevado de Toluca Volcano (Central Mexico), with the description of a new species, Alona manueli sp. nov.

    PubMed

    Sinev, Artem Y; Zawisza, Edyta

    2013-01-01

    Cladoceran communities of two lakes of Nevado de Toluca Volcano, Central Mexico, were studied. A new species of Aloninae, Alona manueli sp. nov., is described. It was previously confused with Palearctic Alona intermedia Sars, 1862, but clearly differs from it in the morphology of postabdomen, head shield and head pores, and thoracic limbs. Position of Alona manueli sp. nov. within the genus is unclear, it did not belong to any species-group within Alona s. lato. Other species recorded in the studied lakes are Alona ossiani Sinev, 1998, Alonella pulchella Herrick, 1884, Chydorus belonging to sphaericus-group, Eurycercus longirostris Hann, 1982 and Pleuroxus cf. denticulatus Birge, 1879. PMID:26295115

  10. Crater studies: Part A: lunar crater morphometry

    USGS Publications Warehouse

    Pike, Richard J.

    1973-01-01

    Morphometry, the quantitative study of shape, complements the visual observation and photointerpretation in analyzing the most outstanding landforms of the Moon, its craters (refs. 32-1 and 32-2). All three of these interpretative tools, which were developed throughout the long history of telescopic lunar study preceding the Apollo Program, will continue to be applicable to crater analysis until detailed field work becomes possible. Although no large (>17.5 km diameter) craters were examined in situ on any of the Apollo landings, the photographs acquired from the command modules will markedly strengthen results of less direct investigations of the craters. For morphometry, the most useful materials are the orbital metric and panoramic photographs from the final three Apollo missions. These photographs permit preparation of contour maps, topographic profiles, and other numerical data that accurately portray for the first time the surface geometry of lunar craters of all sizes. Interpretations of craters no longer need be compromised by inadequate topographic data. In the pre-Apollo era, hypotheses for the genesis of lunar craters usually were constructed without any numerical descriptive data. Such speculations will have little credibility unless supported by accurate, quantitative data, especially those generated from Apollo orbital photographs. This paper presents a general study of the surface geometry of 25 far-side craters and a more detailed study of rim-crest evenness for 15 near-side and far-side craters. Analysis of this preliminary sample of Apollo 15 and 17 data, which includes craters between 1.5 and 275 km in diameter, suggests that most genetic interpretations of craters made from pre-Apollo topographic measurements may require no drastic revision. All measurements were made from topographic profiles generated on a stereoplotter at the Photogrammetric Unit of the U.S. Geological Survey, Center of Astrogeology, Flagstaff, Arizona.

  11. Clays and Sulfates in a Potential Lacustrine Evaporite Sequence at Columbus Crater, Mars

    NASA Astrophysics Data System (ADS)

    Wray, J. J.; Milliken, R. E.; Murchie, S. L.; Swayze, G. A.; Dundas, C. M.; Seelos, F. P.; Squyres, S. W.

    2008-12-01

    From orbit, phyllosilicates and hydrated sulfates on Mars have typically been observed in distinct geographic locales and are thought to record different types of ancient aqueous environments [1]. However, these two mineral classes have recently been found in close association in each of two large impact craters in the Terra Sirenum region of the Southern highlands [2, 3]. In one of these, the D~100 km crater Columbus, CRISM observations show that a polyhydrated non-Fe sulfate is the spatially dominant phase, whereas other distinct layers have spectra consistent with the iron sulfates jarosite and szomolnokite, respectively. Another distinct spectral unit may contain hydrated chloride, or a different non-Fe sulfate. A kaolin group clay is the most commonly detected phyllosilicate, occurring in all CRISM scenes that show the polyhydrated sulfate, but Fe/Mg-phyllosilicates are also seen in small exposures. The polyhydrated sulfate occurs in a light-toned, finely layered, indurated deposit that extends around ~270 degrees of the inner crater wall. The kaolinite unit is commonly stratigraphically beneath the polyhydrated sulfate unit, but some interbedding of the two materials is tentatively observed. Hydrated materials are also present in strata exposed on the crater floor. Kaolinite, sulfates, and chlorides are observed precipitating out of terrestrial acid-saline lakes and ground waters [4], which may be analogs for the environment that deposited the materials in Columbus crater. The overall structure of the deposit is reminiscent of terrestrial "bathtub ring" evaporite deposits. Alternatively, the exposed ring could be part of a preexisting subsurface layer exposed by the impact event; however, the mineral assemblage seen here (kaolinite and polyhydrated sulfate) has not yet been observed in any other craters or intercrater bedrock exposures in the region. Further imaging and topographic data will be used to test the evaporite hypothesis by carefully examining the

  12. Effects of acidic lake water on the eye.

    PubMed

    Basu, P K; Avaria, M; Hasany, S M

    1982-04-01

    The normal eyes of 6 men and 21 rabbits were exposed to samples of lake water, one eye to a sample of pH 4.6 and the other to a sample of pH 6.3. The men's eyes were exposed for 5 minutes on four occasions a week apart, whereas the rabbits' eyes were exposed for 15 minutes either on one occasion or once a day for 7 days. In the humans neither sample of water produced symptoms or signs of an adverse effect on the external eye tissues, apart from brief conjunctival congestion after every exposure. In the rabbits the two samples did not appear, in general, to have different effects on the ocular tissues, as judged from the osmolarity and cell count of the tears, conjunctival congestion, corneal staining with fluorescein, corneal permeability and histologic features of the cornea. In a few instances differences were observed, but their pathological significance was not apparent. These data suggest that lake water of a pH as low as 4.6 may not harm healthy eyes, however, larger and broader studies are essential.

  13. Fish communities in lakes in Subregion 2B (Upper Peninsula of Michigan) in relation to lake acidity. Volume 1 and Volume 2: Appendices. Data tape documentation

    SciTech Connect

    Not Available

    1990-10-01

    The research described in the document represents one component of Phase II of the Eastern Lake Survey (ELS-II), a part of the National Surface Water Survey (NSWS). Surveys of fish community status were conducted in summer 1987 in 49 lakes in ELS Subregion 2B, the Upper Peninsula of Michigan. Subregion 2B was selected because of its (1) high proportion of acidic and low-pH lakes, (2) relative lack of existin data on fish communities in lakes, and (3) diverse geological and hydrological conditions allowing optimal evaluation of the association between lake characteristics and fish community status. A companion study dealing with regional patterns in fish mercury content in Subregion 2B was conducted concurrently; results from the study will be presented in a subsequent report.

  14. Automated Crater Delineation

    NASA Astrophysics Data System (ADS)

    Marques, J. S.; Pina, P.

    2015-05-01

    An algorithm to delineate impact craters based on Edge Maps and Dynamic Programming is presented. The global performance obtained on 1045 craters from Mars (5 m to about 200 km in diameter), achieved 96% of correct contour delineations.

  15. Neutralization of an acidic surface mine lake using organic additives. Final research report, 1 July 1991-1 October 1993

    SciTech Connect

    Brugam, R.B.

    1993-10-01

    We added 9.1 metric tons of manure to a pH 2.9 acid coal mine lake in Southern Illinois to test whether the added organic matter would support sulfate and iron reduction by anaerobic bacteria resulting in the production of alkalinity and a rise in pH. The added organic matter did cause a rise in pH in the deep water of the lake, but the effect did not increase the pH of the whole lake. Experiments in laboratory microcosms at 23 C show that lake sediment treated with manure can permanently raise the pH of acid mine drainage. In the open lake diffusion of oxygen into the anaerobic zones of the water column and low water temperatures in the winter limited the effects of sulfate and iron reduction to the deep water of the lake during summer thermal stratification.

  16. Granite weathering and the sensitivity of alpine lakes to acid deposition

    SciTech Connect

    Stauffer, R.E.

    1990-07-01

    Lake chemical data from the National Surface Water Survey (NSWS) were corrected for the effects of regional atmospheric deposition and then used to evaluate the role of weathering in supplying base cations, silica, sulfate, and alkalinity to surface waters in alpine vs. subalpine, and in glaciated vs. unglaciated granitic terrane of the western and southeastern US. Thermodynamic models, idealized reaction stoichiometry, and multivariate regression involving solutes and geographic variables indicate that irreversible weathering can largely account for lake chemistry. By contrast, relatively minor roles are played by reversible ion exchange in soils and sediments, terrestrial bioaccumulation, and transformation in lakes. The regional patterns in lake acidity components (NO{sub 3}, SO{sub 4}, DOC, CO{sub 2}), and statistical relationships between acidity and base cations demonstrate that rock weathering is limited by acid inputs in many alpine catchments prior to fall overturn. The empirical success of the Henriksen alkalinity model depends on a high Ca: Na weathering ration. The latter increase with increasing physical disturbance of the catchment (juvenility), hence under natural circumstances attains a maximum as a result of on-going or recent glaciation. The Henriksen model fails in geochemically old terrane, where cation losses accompanying silicate weathering attain steady state proportions.

  17. Exploring Impact Crater Paleolakes in 2003

    NASA Astrophysics Data System (ADS)

    Cabrol, N. A.; Grin, E. A.

    2001-01-01

    Paleolakes in impact craters have been surveyed for the past 20 years and have raised considerable interest because of their potential to document many of the questions that are at the heart of the Mars exploration program, especially Astrobiology and search for life. Recent high-resolution Mars Orbiter Camera (MOC) images seem to provide another support to their existence and are giving new data to explore these past lakes that Viking had helped us unravel. They also show the importance of a continuing exploration program at increasing resolution. It is now possible to fully investigate the broad spectrum of martian Crater lakes from Noachian to Amazonian, up to very recent times, since fresh gullies have been also observed in impact craters. Before the confirmation by MOC, several studies on the subject had pointed out the importance of martian limnology as a method to understand the past climate, hydrogeology, and possibly biology of Mars. Considering the questions raised both by the Viking and MGS mission about these crater lakes and their extraordinary potential for astrobiological investigations, the next logical step is to explore them in situ, and it is possible with MER-A and MER-B in 2003.

  18. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    NASA Astrophysics Data System (ADS)

    Marion, G. M.; Crowley, J. K.; Thomson, B. J.; Kargel, J. S.; Bridges, N. T.; Hook, S. J.; Baldridge, A.; Brown, A. J.; Ribeiro da Luz, B.; de Souza Filho, C. R.

    2009-06-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (<0 °C), if possible, and (3) use the reformulated model to investigate parallels in the mineral precipitation behavior of acidic Australian lakes and hypothetical Martian brines. FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the Pitzer approach for the temperature range from <-70 to 25 °C and the pressure range from 1 to 1000 bars. Aluminum chloride and sulfate mineral parameterizations were based on experimental data. Aluminum hydroxide and silicon mineral parameterizations were based on Gibbs free energy and enthalpy data. New aluminum and silicon parameterizations added 12 new aluminum/silicon minerals to this Na-K-Mg-Ca-Fe(II)-Fe(III)-Al-H-Cl-Br-SO 4-NO 3-OH-HCO 3-CO 3-CO 2-O 2-CH 4-Si-H 2O system that now contain 95 solid phases. There were similarities, differences, and uncertainties between Australian acidic, saline playa lakes and waters that likely led to the Burns formation salt accumulations on Mars. Both systems are similar in that they are dominated by (1) acidic, saline ground waters and sediments, (2) Ca and/or Mg sulfates, and (3) iron

  19. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    USGS Publications Warehouse

    Marion, G.M.; Crowley, J.K.; Thomson, B.J.; Kargel, J.S.; Bridges, N.T.; Hook, S.J.; Baldridge, A.; Brown, A.J.; Ribeiro da Luz, B.; de Souza, Filho C.R.

    2009-01-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (<0 ??C), if possible, and (3) use the reformulated model to investigate parallels in the mineral precipitation behavior of acidic Australian lakes and hypothetical Martian brines. FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the Pitzer approach for the temperature range from <-70 to 25 ??C and the pressure range from 1 to 1000 bars. Aluminum chloride and sulfate mineral parameterizations were based on experimental data. Aluminum hydroxide and silicon mineral parameterizations were based on Gibbs free energy and enthalpy data. New aluminum and silicon parameterizations added 12 new aluminum/silicon minerals to this Na-K-Mg-Ca-Fe(II)-Fe(III)-Al-H-Cl-Br-SO4-NO3-OH-HCO3-CO3-CO2-O2-CH4-Si-H2O system that now contain 95 solid phases. There were similarities, differences, and uncertainties between Australian acidic, saline playa lakes and waters that likely led to the Burns formation salt accumulations on Mars. Both systems are similar in that they are dominated by (1) acidic, saline ground waters and sediments, (2) Ca and/or Mg sulfates, and (3) iron

  20. Degraded Crater Rim

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 3 May 2002) The Science The eastern rim of this unnamed crater in Southern Arabia Terra is very degraded (beaten up). This indicates that this crater is very ancient and has been subjected to erosion and subsequent bombardment from other impactors such as asteroids and comets. One of these later (younger) craters is seen in the upper right of this image superimposed upon the older crater rim material. Note that this smaller younger crater rim is sharper and more intact than the older crater rim. This region is also mantled with a blanket of dust. This dust mantle causes the underlying topography to take on a more subdued appearance. The Story When you think of Arabia, you probably think of hot deserts and a lot of profitable oil reserves. On Mars, however, Southern Arabia Terra is a cold place of cratered terrain. This almost frothy-looking image is the badly battered edge of an ancient crater, which has suffered both erosion and bombardment from asteroids, comets, or other impacting bodies over the long course of its existence. A blanket of dust has also settled over the region, which gives the otherwise rugged landscape a soft and more subdued appearance. The small, round crater (upper left) seems almost gemlike in its setting against the larger crater ring. But this companionship is no easy romance. Whatever formed the small crater clearly whammed into the larger crater rim at some point, obliterating part of its edge. You can tell the small crater was formed after the first and more devastating impact, because it is laid over the other larger crater. How much younger is the small one? Well, its rim is also much sharper and more intact, which gives a sense that it is probably far more youthful than the very degraded, ancient crater.

  1. Impact craters on Titan

    USGS Publications Warehouse

    Wood, C.A.; Lorenz, R.; Kirk, R.; Lopes, R.; Mitchell, Ken; Stofan, E.

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles. ?? 2009 Elsevier Inc.

  2. Impact craters on Titan

    USGS Publications Warehouse

    Wood, Charles A.; Lorenz, Ralph; Kirk, Randy; Lopes, Rosaly; Mitchell, Karl; Stofan, Ellen; ,

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles.

  3. Pathways of acid mine drainage to Clear Lake: implications for mercury cycling.

    PubMed

    Shipp, William G; Zierenberg, Robert A

    2008-12-01

    Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (> or =197 mmol/L), aluminum (> or =52 mmol/L), and iron (> or =28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sulfide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg+2, making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 per thousand) and highly depleted isotope values for diagenetic pyrite (as low as -22.6 per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake

  4. Pathways of acid mine drainage to Clear Lake: implications for mercury cycling.

    PubMed

    Shipp, William G; Zierenberg, Robert A

    2008-12-01

    Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (> or =197 mmol/L), aluminum (> or =52 mmol/L), and iron (> or =28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sulfide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg+2, making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 per thousand) and highly depleted isotope values for diagenetic pyrite (as low as -22.6 per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake

  5. Distribution of Dehalococcoidia in the Anaerobic Deep Water of a Remote Meromictic Crater Lake and Detection of Dehalococcoidia-Derived Reductive Dehalogenase Homologous Genes.

    PubMed

    Biderre-Petit, Corinne; Dugat-Bony, Eric; Mege, Mickaël; Parisot, Nicolas; Adrian, Lorenz; Moné, Anne; Denonfoux, Jérémie; Peyretaillade, Eric; Debroas, Didier; Boucher, Delphine; Peyret, Pierre

    2016-01-01

    Here we describe the natural occurrence of bacteria of the class Dehalococcoidia (DEH) and their diversity at different depths in anoxic waters of a remote meromictic lake (Lake Pavin) using 16S rRNA gene amplicon sequencing and quantitative PCR. Detected DEH are phylogenetically diverse and the majority of 16S rRNA sequences have less than 91% similarity to previously isolated DEH 16S rRNA sequences. To predict the metabolic potential of detected DEH subgroups and to assess if they encode genes to transform halogenated compounds, we enriched DEH-affiliated genomic DNA by using a specific-gene capture method and probes against DEH-derived 16S rRNA genes, reductive dehalogenase genes and known insertion sequences. Two reductive dehalogenase homologous sequences were identified from DEH-enriched genomic DNA, and marker genes in the direct vicinity confirm that gene fragments were derived from DEH. The low sequence similarity with known reductive dehalogenase genes suggests yet-unknown catabolic potential in the anoxic zone of Lake Pavin. PMID:26734727

  6. Distribution of Dehalococcoidia in the Anaerobic Deep Water of a Remote Meromictic Crater Lake and Detection of Dehalococcoidia-Derived Reductive Dehalogenase Homologous Genes.

    PubMed

    Biderre-Petit, Corinne; Dugat-Bony, Eric; Mege, Mickaël; Parisot, Nicolas; Adrian, Lorenz; Moné, Anne; Denonfoux, Jérémie; Peyretaillade, Eric; Debroas, Didier; Boucher, Delphine; Peyret, Pierre

    2016-01-01

    Here we describe the natural occurrence of bacteria of the class Dehalococcoidia (DEH) and their diversity at different depths in anoxic waters of a remote meromictic lake (Lake Pavin) using 16S rRNA gene amplicon sequencing and quantitative PCR. Detected DEH are phylogenetically diverse and the majority of 16S rRNA sequences have less than 91% similarity to previously isolated DEH 16S rRNA sequences. To predict the metabolic potential of detected DEH subgroups and to assess if they encode genes to transform halogenated compounds, we enriched DEH-affiliated genomic DNA by using a specific-gene capture method and probes against DEH-derived 16S rRNA genes, reductive dehalogenase genes and known insertion sequences. Two reductive dehalogenase homologous sequences were identified from DEH-enriched genomic DNA, and marker genes in the direct vicinity confirm that gene fragments were derived from DEH. The low sequence similarity with known reductive dehalogenase genes suggests yet-unknown catabolic potential in the anoxic zone of Lake Pavin.

  7. Distribution of Dehalococcoidia in the Anaerobic Deep Water of a Remote Meromictic Crater Lake and Detection of Dehalococcoidia-Derived Reductive Dehalogenase Homologous Genes

    PubMed Central

    Biderre-Petit, Corinne; Dugat-Bony, Eric; Mege, Mickaël; Parisot, Nicolas; Adrian, Lorenz; Moné, Anne; Denonfoux, Jérémie; Peyretaillade, Eric; Debroas, Didier; Boucher, Delphine; Peyret, Pierre

    2016-01-01

    Here we describe the natural occurrence of bacteria of the class Dehalococcoidia (DEH) and their diversity at different depths in anoxic waters of a remote meromictic lake (Lake Pavin) using 16S rRNA gene amplicon sequencing and quantitative PCR. Detected DEH are phylogenetically diverse and the majority of 16S rRNA sequences have less than 91% similarity to previously isolated DEH 16S rRNA sequences. To predict the metabolic potential of detected DEH subgroups and to assess if they encode genes to transform halogenated compounds, we enriched DEH-affiliated genomic DNA by using a specific-gene capture method and probes against DEH-derived 16S rRNA genes, reductive dehalogenase genes and known insertion sequences. Two reductive dehalogenase homologous sequences were identified from DEH-enriched genomic DNA, and marker genes in the direct vicinity confirm that gene fragments were derived from DEH. The low sequence similarity with known reductive dehalogenase genes suggests yet-unknown catabolic potential in the anoxic zone of Lake Pavin. PMID:26734727

  8. Algal and Bacterial Activities in Acidic (pH 3) Strip Mine Lakes

    PubMed Central

    Gyure, Ruth A.; Konopka, Allan; Brooks, Austin; Doemel, William

    1987-01-01

    Reservoir 29 and Lake B are extremely acid lakes (epilimnion pHs of 2.7 and 3.2, respectively), because they receive acidic discharges from coal refuse piles. They differ in that the pH of profundal sediments in Reservoir 29 increased from 2.7 to 3.8 during the period of thermal stratification, whereas permanently anoxic sediments in Lake B had a pH of 6.2. The pH rise in Reservoir 29 sediments was correlated with a temporal increase in H2S concentration in the anaerobic hypolimnion from 0 to >1 mM. The chlorophyll a levels in the epilimnion of Reservoir 29 were low, and the rate of primary production was typical of an oligotrophic system. However, there was a dense 10-cm layer of algal biomass at the bottom of the metalimnion. Production by this layer was low owing to light limitation and possibly H2S toxicity. The specific photosynthetic rates of epilimnetic algae were low, which suggests that nutrient availability is more important than pH in limiting production. The highest photosynthetic rates were obtained in water samples incubated at pH 2.7 to 4. Heterotrophic bacterial activity (measured by [14C]glucose metabolism) was greatest at the sediment/water interface. Bacterial production (assayed by thymidine incorporation) was as high in Reservoir 29 as in a nonacid mesotrophic Indiana lake. PMID:16347430

  9. Algal and bacterial activities in acidic (pH 3) strip mine lakes

    SciTech Connect

    Gyure, R.A.; Konopka, A.; Brooks, A.; Doemel, W.

    1987-09-01

    Reservoir 29 and Lake B are extremely acid lakes (epilimnion pHs of 2.7 and 3.2, respectively), because they receive acidic discharges from coal refuse piles. They differ in that the pH of profundal sediments in Reservoir 29 increased from 2.7 to 3.8 during the period of thermal stratification, whereas permanently anoxic sediments in Lake B had a pH of 6.2. The pH rise in Reservoir 29 sediments was correlated with a temporal increase in H/sub 2/S concentration in the anaerobic hypolimnion from 0 to >1 mM. The chlorophyll a levels in the epilimnion of Reservoir 29 were low, and the rate of primary production was typical of an oligotrophic system. However, there was a dense 10-cm layer of algal biomass at the bottom of the metalimnion. Production by this layer was low owing to light limitation and possibly H/sub 2/S toxicity. The specific photosynthetic rates of epilimnetic algae were low, which suggests that nutrient availability is more important than pH in limiting production. The highest photosynthetic rates were obtained in water samples incubated at pH 2.7 to 4. Heterotrophic bacterial activity (measured by (/sup 14/C)glucose metabolism) was greatest at the sediment/water interface. Bacterial production (assayed by thymidine incorporation) was as high in Reservoir 29 as in a nonacid mesotrophic Indiana lake.

  10. Marine-target craters on Mars? An assessment study

    USGS Publications Warehouse

    Ormo, J.; Dohm, J.M.; Ferris, J.C.; Lepinette, A.; Fairen, A.G.

    2004-01-01

    Observations of impact craters on Earth show that a water column at the target strongly influences lithology and morphology of the resultant crater. The degree of influence varies with the target water depth and impactor diameter. Morphological features detectable in satellite imagery include a concentric shape with an inner crater inset within a shallower outer crater, which is cut by gullies excavated by the resurge of water. In this study, we show that if oceans, large seas, and lakes existed on Mars for periods of time, marine-target craters must have formed. We make an assessment of the minimum and maximum amounts of such craters based on published data on water depths, extent, and duration of putative oceans within "contacts 1 and 2," cratering rate during the different oceanic phases, and computer modeling of minimum impactor diameters required to form long-lasting craters in the seafloor of the oceans. We also discuss the influence of erosion and sedimentation on the preservation and exposure of the craters. For an ocean within the smaller "contact 2" with a duration of 100,000 yr and the low present crater formation rate, only ???1-2 detectable marine-target craters would have formed. In a maximum estimate with a duration of 0.8 Gyr, as many as 1400 craters may have formed. An ocean within the larger "contact 1-Meridiani," with a duration of 100,000 yr, would not have received any seafloor craters despite the higher crater formation rate estimated before 3.5 Gyr. On the other hand, with a maximum duration of 0.8 Gyr, about 160 seafloor craters may have formed. However, terrestrial examples show that most marine-target craters may be covered by thick sediments. Ground penetrating radar surveys planned for the ESA Mars Express and NASA 2005 missions may reveal buried craters, though it is uncertain if the resolution will allow the detection of diagnostic features of marine-target craters. The implications regarding the discovery of marine-target craters on

  11. Survey of duckweed diversity in Lake Chao and total fatty acid, triacylglycerol, profiles of representative strains.

    PubMed

    Tang, J; Li, Y; Ma, J; Cheng, J J

    2015-09-01

    Lemnaceae (duckweeds) are widely distributed aquatic flowering plants. Their high growth rate, starch content and suitability for bioremediation make them potential feedstock for biofuels. However, few natural duckweed resources have been investigated in China, and there is no information about total fatty acid (TFA) and triacylglycerol (TAG) composition of duckweeds from China. Here, the genetic diversity of a natural duckweed population collected from Lake Chao, China, was investigated using multilocus sequence typing (MLST). The 54 strains were categorised into four species in four genera, representing 12 distinct sequence types. Strains representing Lemna aequinoctialis and Spirodela polyrhiza were predominant. Interestingly, a surprisingly high degree of genetic diversification within L. aequinoctialis was observed. The four duckweed species revealed a uniform fatty acid composition, with three fatty acids, palmitic acid, linoleic acid and linolenic acid, accounting for more than 80% of the TFA. The TFA in biomass varied among species, ranging from 1.05% (of dry weight, DW) for L. punctata and S. polyrhiza to 1.62% for Wolffia globosa. The four duckweed species contained similar TAG contents, 0.02% mg · DW(-1). The fatty acid profiles of TAG were different from those of TFA, and also varied among the four species. The survey investigated the genetic diversity of duckweeds from Lake Chao, and provides an initial insight into TFA and TAG of four duckweed species, indicating that intraspecific and interspecific variations exist in the content and composition of both TFA and TAG in comparison with other studies.

  12. Local variations of bulk hydrogen and chlorine content measured at the contact between the Sheepbed and Gillespie Lake units in Yellowknife Bay, Gale Crater, using the DAN instrument onboard Curiosity

    NASA Astrophysics Data System (ADS)

    litvak, M. L.; Mitrofanov, I. G.; Behar, A.; Boynton, W. V.; DeFlores, L.; Fedosov, F.; Golovin, D.; Hardgrove, C. J.; Harshman, K.; Kozyrev, A.; Jun, I.; Kuzmin, R.; Lisov, D.; Malakhov, A.; Milliken, R.; Mischna, M. A.; Moersch, J.; Mokrousov, M.; Nikiforov, S.; Sanin, A.; Shvetsov, V.; Starr, R. D.; Tate, C.; Tretyakov, V.; Vostrukhin, A.; Team, M.

    2013-12-01

    The Curiosity rover successfully landed on Aug 6, 2012, at Gale crater and immediately started continuous surface observations of the surrounding environment at the landing site and then along the rover's traverse. The search for aqueous environments and study of their evolution is considered to be a high priority science activity during these observations. In this paper we have focused on the one aspect of this task related to monitoring local variations of hydrogen distribution in the subsurface at the small horizontal scale of 1-10 m based on neutron spectroscopic methods. This was accomplished using data gathered by the Dynamic Albedo of Neutron (DAN) instrument. These data were specially acquired during the rover's traverse inside a location known as Yellowknife Bay. This campaign was specially organized to test the potential variability of water bulk content across the geologic contact between Sheepbed unit mudstones (the primary target for drilling contact science) and the Gillespie Lake unit (upper unit above Sheepbed). The observation program consisted of a dedicated traverse route selected to being in a position at the drilling sites named John Klein and Cumberland, and then drive up to the contact between Sheepbed and Gillespie, making stops every 0.75-1 m to perform high SNR active neutron measurements. The end of traverse was planned several meters past the contact and the total length of the traverse is estimated to be about 20 m.

  13. Mineralogy of the Pahrump Hills Region, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Ming, D. W.; Vaniman, D. T.; Blake, D. F.; Chipera, S. J.; Morris, R. V.; Bish, D. L.; Cavanagh, P. D.; Achilles, C. N.; Bristow, T. F.; Morrison, S. M.; Treiman, A. H.; Downs, R. T.; Farmer, J. D.; Crisp, J. A.; Fendrich, K.; Morookian, J. M.

    2015-01-01

    The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rocks in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September, 2014, and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three rock samples to its internal instruments, including the CheMin XRD/XRF. The three targets, Confidence Hills, Mojave 2, and Telegraph Peak, contain variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, and X-ray amorphous material. Hematite was predicted at the base of Mount Sharp from orbital visible/near-IR spectroscopy, and CheMin confirmed this detection. The presence of jarosite throughout Pahrump Hills suggests the sediments experienced acid-sulfate alteration, either in-situ or within the source region of the sediments. This acidic leaching environment is in stark contrast to the environment preserved within the Sheepbed mudstone on the plains of Gale crater. The minerals within Sheepbed, including Fe-saponite, indicate these sediments were deposited in a shallow lake with circumneutral pH that may have been habitable.

  14. Australian Acid Playa Lake as a Mars Analog: Results from Sediment Lipid Analysis

    NASA Astrophysics Data System (ADS)

    Graham, H.; Baldridge, A. M.; Stern, J. C.

    2015-12-01

    The ephemeral saline acidic lakes on the Yilgarn Craton of Western Australia have been suggested as geochemical analogues to martian terrains. Both are characterized by interbedded phyllosilicates and hydrated sulfates. On Mars, these areas indicate shifting environmental conditions, from the neutral/alkaline and wet conditions that dominated during the Noachian era to the more familiar dry, acidic conditions that began in the Hesperian. The habitability of such a dynamic environment can be informed by investigation of the Yilgarn Lake system. Previous work has found phospholipid fatty acids (PLFA) evidence of microbial communities in sections of sediment cores taken from Lake Gilmore. These communities include both Gram-positive and -negative bacteria, Actinomycetes, and even methanotrophs. Given recurring detection of methane on the martian surface, evidence of a methane cycling community in an analogous environment is of particular interest. In this study we analyze the carbon isotope composition of bulk organic material as well as extracted lipids from the Lake Gilmore sediment cores at both a near-shore and mid-lake location. These analyses reveal very low accumulations of organic carbon, concentrated primarily in the gypsum-rich near-shore core. The near-shore sediments show a down-core decrease in abundance of organic carbon as well as depletion in the carbon isotope composition (δ13C) with depth. Bulk carbon did not exhibit the unique, highly depleted, diagnostic signature associated with methanotrophic biomass. Compound-specific isotope analysis (CSIA) of carbon in extracted methanotroph PFLAs can confirm the presence of a methane cycling metabolism at depth. Also, additional extractions have isolated lipids associated with lake-edge grasses. These analyses consider both the chain-length distribution and carbon CSIA of these lipids in order to understand the effect of terrestrial detritus on any preserved methanotroph carbon signal, given the very low

  15. Assessing the effectiveness of federal acid rain policy using remote and high elevation lakes in northern New England

    NASA Astrophysics Data System (ADS)

    Baumann, Adam J.

    The 1990 U.S. Clean Air Act Amendments (CAAA) set target reductions for both sulfur and nitrogen emissions to reduce acidic deposition and improve the biologically-relevant chemistry of low ANC surface waters in the United States. The Maine High Elevation Lake Monitoring (HELM) project was designed to complement other acid rain status and trend assessments in the northeast that were known to have underestimated the number of acidic lakes. HELM lakes are more susceptible to the effects of acid deposition than lowland lakes typically included in other surveys because they receive higher amounts of precipitation, and the watersheds are less able to neutralize acidic inputs because of steep slopes, shallow soils, and resistant bedrock. Furthermore, development impacts that affect water quality and cloud our interpretation of recovery from deposition in many lowland lakes are absent in the HELM lakes. Since 1986, HELM surface water SO4-2 concentration has decreased at a rate of 1.6mueq/L/yr.. HELM lake ANC has increased at a rate of 0.58 mueq/L/yr. and hydrogen ion has decreased at a rate of 0.05 mueq/L/yr. since 1986, highlighting the positive effect the CAAA is having on HELM acidity. Over the same time period, HELM DOC has increased at rate of 0.03 mg/L/yr., raising the median DOC in HELM lakes by 21%. Furthermore, we calculate that organic anions (OA-) now contribute 10% to 15% more to total anionic charge while at the same time, the lakes have become 23% more dilute. The increase in DOC has led to a shift in the source of acidity from anthropogenic inorganic (acid rain), to natural organic DOC sources. While this shift appears to complicate the interpretation of acid-base data coming from acid-sensitive lakes, in reality it highlights recovery to a more natural state for these surface waters. A comparison of HELM recovery data to recent data from the New Hampshire Remote Pond (NHRP) project serves to put the NHRP in regional perspective as well as enabling us to

  16. Anthropogenically driven changes in chloride complicate interpretation of base cation trends in lakes recovering from acidic deposition.

    PubMed

    Rosfjord, Catherine H; Webster, Katherine E; Kahl, Jeffrey S; Norton, Stephen A; Fernandez, Ivan J; Herlihy, Alan T

    2007-11-15

    Declines in Ca and Mg in low ANC lakes recovering from acidic deposition are widespread across the northern hemisphere. We report overall increases between 1984 and 2004 in the concentrations of Ca + Mg and Cl in lakes representing the statistical population of nearly 4000 low ANC lakes in the northeast U.S. Increases in Cl occurred in nearly all lakes in urbanized southern New England, but only 18% of lakes in more remote Maine had Cl increases. This spatial pattern implicates road salt application as the major source of the increased Cl salts. Among the 48% of the lake population classified as salt-affected, the median changes in Cl (+133 microeq/L) and Ca + Mg (+47 microeq/ L) were large and positive in direction over the 20 years. However, in the unaffected lakes, Cl remained stable and Ca + Mg decreased (-3 microeq/L), consistent with reported long-term trends in base cations of acid-sensitive lakes. This discrepancy between the Cl groups suggests that changes in ion exchange processes in salt-affected watersheds have altered the geochemical cycling of Ca and Mg. One policy-relevant implication is that waters influenced by Cl salts complicate regional assessments of surface water recovery from "acid rain" related to the passage of the Clean Air Act.

  17. Simulated Craters on Venus

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    The thick atmosphere of Venus prevents all but the largest impactors from cratering the surface. The number of small craters on Venus provides an interesting, and statistically significant test of models for the disruption and deceleration of impacting bodies. Here we compare Monte Carlo simulated crater distributions to the observed crater distribution on Venus. The simulation assumes: (1) a power law mass distribution for impactors of the form N(sub cum) alpha m (exp-b) where b=0.8; (2) isotropic incidence angles; (3) velocity at the top of the atmosphere of 20 kilometers per second (more realistic velocity distributions are also considered); (4) Schmidt-Housen crater scaling, modified such that only the normal component of the impact velocity contributes to cratering, and using crater slumping as parameterized (5) and modern populations (60% carbonaceous, 40% stone, 3% iron) and fluxes of asteroids. We use our previously developed model for the disruption and deceleration of large bodies striking thick planetary atmospheres to calculate the impact velocity at the surface as a function of impactor mass, incident velocity, and incident angle. We use a drag coefficient c(sub d) =1; other parameters are as described in Chyba et al. We set a low velocity cutoff of 500 meters per second on crater-forming impacts. Venus's craters are nicely matched by the simulated craters produced by 700 million years of striking asteroids. Shown for comparison are the simulated craters produced by incident comets over the same period, where for comets we have assumed b=0.7 and a flux at 10(exp 14) g 30% that of asteroids. Systematic uncertainties in crater scaling and crater slumping may make the surface age uncertain by a factor of two.

  18. Strong assortative mating by diet, color, size, and morphology but limited progress toward sympatric speciation in a classic example: Cameroon crater lake cichlids.

    PubMed

    Martin, Christopher H

    2013-07-01

    Models predict that sympatric speciation depends on restrictive parameter ranges, such as sufficiently strong disruptive selection and assortative mating, but compelling examples in nature have rarely been used to test these predictions. I measured the strength of assortative mating within a species complex of Tilapia in Lake Ejagham, Cameroon, a celebrated example of incipient sympatric adaptive radiation. This species complex is in the earliest stages of speciation: morphological and ecological divergence are incomplete, species differ primarily in breeding coloration, and introgression is common. I captured 27 mated pairs in situ and measured the diet, color, size, and morphology of each individual. I found strong assortative mating by color, size, head depth, and dietary source of benthic or pelagic prey along two independent dimensions of assortment. Thus, Ejagham Tilapia showed strong assortative mating most conducive to sympatric speciation. Nonetheless, in contrast to a morphologically bimodal Sarotherodon cichlid species pair in the lake, Ejagham Tilapia show more limited progress toward speciation, likely due to insufficient strength of disruptive selection on morphology estimated in a previous study (γ = 0.16). This supports the predicted dependence of sympatric speciation on strong assortment and strong disruptive selection by examining a potentially stalled example in nature.

  19. Long-term recovery of lakes in the Adirondack region of New York to decreases in acidic deposition

    NASA Astrophysics Data System (ADS)

    Waller, Kristin; Driscoll, Charles; Lynch, Jason; Newcomb, Dani; Roy, Karen

    2012-01-01

    After years of adverse impacts to the acid-sensitive ecosystems of the eastern United States, the Acid Rain Program and Nitrogen Budget Program were developed to control sulfur dioxide (SO 2) and nitrogen oxide (NO x) emissions through market-based cap and trade systems. We used data from the National Atmospheric Deposition Program's National Trends Network (NTN) and the U.S. EPA Temporally Integrated Monitoring of Ecosystems (TIME) program to evaluate the response of lake-watersheds in the Adirondack region of New York to changes in emissions of sulfur dioxide and nitrogen oxides resulting from the Acid Rain Program and the Nitrogen Budget Program. TIME is a long-term monitoring program designed to sample statistically selected subpopulations of lakes and streams across the eastern U.S. to quantify regional trends in surface water chemistry due to changes in atmospheric deposition. Decreases in wet sulfate deposition for the TIME lake-watersheds from 1991 to 2007 (-1.04 meq m -2-yr) generally corresponded with decreases in estimated lake sulfate flux (-1.46 ± 0.72 meq m -2-yr), suggesting declines in lake sulfate were largely driven by decreases in atmospheric deposition. Decreases in lake sulfate and to a lesser extent nitrate have generally coincided with increases in acid neutralizing capacity (ANC) resulting in shifts in lakes among ANC sensitivity classes. The percentage of acidic Adirondack lakes (ANC <0 μeq L -1) decreased from 15.5% (284 lakes) to 8.3% (152 lakes) since the implementation of the Acid Rain Program and the Nitrogen Budget Program. Two measures of ANC were considered in our analysis: ANC determined directly by Gran plot analysis (ANC G) and ANC calculated by major ion chemistry (ANC calc = CB - CA). While these two metrics should theoretically show similar responses, ANC calc (+2.03 μeq L -1-yr) increased at more than twice the rate as ANC G (+0.76 μeq L -1-yr). This discrepancy has important implications for assessments of lake recovery

  20. Trends in summer chemistry linked to productivity in lakes recovering from acid deposition in the Adirondack region of New York

    USGS Publications Warehouse

    Momen, B.; Lawrence, G.B.; Nierzwicki-Bauer, S. A.; Sutherland, J.W.; Eichler, L.W.; Harrison, J.P.; Boylen, C.W.

    2006-01-01

    The US Environmental Protection Agency established the Adirondack Effects Assessment Program (AEAP) to evaluate and monitor the status of biological communities in lakes in the Adirondack region of New York that have been adversely affected by acid deposition. This program includes chemical analysis of 30 lakes, sampled two to three times each summer. Results of trends analysis for lake chemistry and chlorophyll a (chlor a) are presented for 1994 to 2003, and a general comparison is made with recent results of the Adirondack Long-Term Monitoring (ALTM) Program, which included chemical analysis of all but two of these lakes (plus an additional 24 lakes) monthly, year-round for 1992-2004. Increases in pH were found in 25 of the 30 AEAP lakes (P < 0.05) and increases in acid-neutralizing capacity (ANC) were found in 12 of the 30 lakes (P < 0.05). Concentrations of both SO 42- and Mg 2+ decreased in 11 lakes (P < 0.05), whereas concentrations of NO 3- decreased in 20 lakes (P < 0.05). Concentrations of NH 4+ decreased in 10 lakes at a significance level of P < 0.05 and in three other lakes based on P < 0.1. Concentrations of inorganic and organic monomeric aluminum generally were below the reporting limit of 1.5 ??mol L-1, but decreases were detected in four and five lakes, respectively (P < 0.1). Concentrations of chlor a increased in seven lakes at a significance level of P < 0.05 and two lakes at a significance level of P < 0.1. A significant inverse correlation was also found between chlor a and NO 3- concentrations in nine lakes at a significance level of P < 0.05 and two lakes at a significance level of P < 0.1. Results of AEAP analysis of lake chemistry were similar to those of the ALTM Program, although decreases in SO 42- concentrations were more evident in the year-round ALTM record. Overall, the results suggest (a) a degree of chemical recovery from acidification during the summer, (b) an increase in phytoplankton productivity, and (c) a decreasing trend in

  1. Responses of 20 lake-watersheds in the Adirondack region of New York to historical and potential future acidic deposition.

    PubMed

    Zhou, Qingtao; Driscoll, Charles T; Sullivan, Timothy J

    2015-04-01

    Critical loads (CLs) and dynamic critical loads (DCLs) are important tools to guide the protection of ecosystems from air pollution. In order to quantify decreases in acidic deposition necessary to protect sensitive aquatic species, we calculated CLs and DCLs of sulfate (SO4(2-))+nitrate (NO3-) for 20 lake-watersheds from the Adirondack region of New York using the dynamic model, PnET-BGC. We evaluated lake water chemistry and fish and total zooplankton species richness in response to historical acidic deposition and under future deposition scenarios. The model performed well in simulating measured chemistry of Adirondack lakes. Current deposition of SO4(2-)+NO3-, calcium (Ca2+) weathering rate and lake acid neutralizing capacity (ANC) in 1850 were related to the extent of historical acidification (1850-2008). Changes in lake Al3+ concentrations since the onset of acidic deposition were also related to Ca2+ weathering rate and ANC in 1850. Lake ANC and fish and total zooplankton species richness were projected to increase under hypothetical decreases in future deposition. However, model projections suggest that lake ecosystems will not achieve complete chemical and biological recovery in the future.

  2. Impact craters on Venus

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.

    1991-01-01

    Compared with volcanism and tectonism, impact cratering on Venus has played an overall minor role in sculpting the present-day landscape. The study of Venus impact craters is vital to help place the chronology of the geologic features on the surface in the context of the planet's geological evolution. The degradation of impact craters also provides information on surface and interior processes, particularly alteration by tectonism and volcanism. Through orbit 1422, Magellan mapped about 450 impact craters, with diameters ranging from 2 to 275 km, within an area of about 226 million sq km, or 49 percent of the planet's surface. These craters and their associated deposits show surprisingly little evidence of degradation at the 75 m/pixel resolution of the Magellan SAR. Remarkably few craters in the Magellan images appear to be in the process of being buried by volcanic deposits or destroyed by tectonic activity.

  3. Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition.

    PubMed

    Jeffries, Dean S; Clair, Thomas A; Couture, Suzanne; Dillon, Peter J; Dupont, Jacques; Keller, Wendel; McNicol, Donald K; Turner, Michael A; Vet, Robert; Weeber, Russell

    2003-04-01

    Reductions in North American sulfur dioxide (SO2) emissions promoted expectations that aquatic ecosystems in southeastern Canada would soon recover from acidification. Only lakes located near smelters that have dramatically reduced emissions approach this expectation. Lakes in the Atlantic provinces, Quebec and Ontario affected only by long-range sources show a general decline in sulfate (SO4(2-)) concentrations, but with a relatively smaller compensating increase in pH or alkalinity. Several factors may contribute to the constrained (or most likely delayed) acidity response: declining base cation concentrations, drought-induced mobilization of SO4(2-), damaged internal alkalinity generation mechanisms, and perhaps increasing nitrate or organic anion levels. Monitoring to detect biological recovery in southeastern Canada is extremely limited, but where it occurs, there is little evidence of recovery outside of the Sudbury/Killarney area. Both the occurrence of Atlantic salmon in Nova Scotia rivers and the breeding success of Common Loons in Ontario lakes are in fact declining although factors beyond acidification also play a role. Chemical and biological models predict that much greater SO2 emission reductions than those presently required by legislation will be needed to promote widespread chemical and latterly, biological recovery. It may be unrealistic to expect that pre-industrial chemical and biological conditions can ever be reestablished in many lakes of southeastern Canada.

  4. Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition.

    PubMed

    Jeffries, Dean S; Clair, Thomas A; Couture, Suzanne; Dillon, Peter J; Dupont, Jacques; Keller, Wendel; McNicol, Donald K; Turner, Michael A; Vet, Robert; Weeber, Russell

    2003-04-01

    Reductions in North American sulfur dioxide (SO2) emissions promoted expectations that aquatic ecosystems in southeastern Canada would soon recover from acidification. Only lakes located near smelters that have dramatically reduced emissions approach this expectation. Lakes in the Atlantic provinces, Quebec and Ontario affected only by long-range sources show a general decline in sulfate (SO4(2-)) concentrations, but with a relatively smaller compensating increase in pH or alkalinity. Several factors may contribute to the constrained (or most likely delayed) acidity response: declining base cation concentrations, drought-induced mobilization of SO4(2-), damaged internal alkalinity generation mechanisms, and perhaps increasing nitrate or organic anion levels. Monitoring to detect biological recovery in southeastern Canada is extremely limited, but where it occurs, there is little evidence of recovery outside of the Sudbury/Killarney area. Both the occurrence of Atlantic salmon in Nova Scotia rivers and the breeding success of Common Loons in Ontario lakes are in fact declining although factors beyond acidification also play a role. Chemical and biological models predict that much greater SO2 emission reductions than those presently required by legislation will be needed to promote widespread chemical and latterly, biological recovery. It may be unrealistic to expect that pre-industrial chemical and biological conditions can ever be reestablished in many lakes of southeastern Canada. PMID:12839192

  5. Late Holocene Sediment Study From Santa María del Oro Crater Lake, Nayarit, México, Using Environmental Magnetism

    NASA Astrophysics Data System (ADS)

    Vazquez, G.; Ortega, B.; Rodriguez, A.

    2007-05-01

    The lake is located near the Pacific coast of Mexico, at the western end of the Trans Mexican Volcanic Belt. It is a deep lake (ca. 65 m) with steep sides and only a small bay (Agua Caliente) has shallower water (ca. 12 m). Four parallel cores between 4 and 9 m long were recovered in March 2002 from this shallower area. Sediments are characterized by alternated laminations (few millimeters to 2 cm) of sand, brown silt, green silt, reddish silt, ochre silt, and peat. The 14-C dated sequence spans the last ca. 2,600 yrs. Given this age, it is possible that each set of laminations represent annual sedimentation cycles. The record is a potential high- resolution archive of environmental and climatic variability for western Mexico for late Holocene. Magnetic measurements of susceptibility along the cores show a high variability in the concentration of magnetic mineralogy. Different magnetic and non-magnetic properties show two sets of facies in relation to its magnetic mineralogy; one group composed by sand, brown silt, green silt and peat has the magnetite and Ti-magnetite as the principal magnetic phase; the second group, composed by reddish and ochre silt, has a low Ti magnetite component and siderite, as the principal paramagnetic component. The effects of climatic variations such as the drought occurred in the archeological Classic period (100 - 900 dC), the Medieval Warm Period (950 - 1350 dC), the Little Ice Age (1400 - 1800 dC), and the droughts over the last 700 years, documented in sites along central Mexico, are recognized in the magnetic mineralogy of Santa Maria del Oro.

  6. Perfluoroalkyl acids in the egg yolk of birds from Lake Shihwa, Korea.

    PubMed

    Yoo, Hoon; Kannan, Kurunthachalam; Kim, Seong Kyu; Lee, Kyu Tae; Newsted, John L; Giesy, John P

    2008-08-01

    Concentrations of perfluoroalkyl acids (PFAs) were measured in egg yolks of three species of birds, the little egret (Egretta garzetta), little ringed plover (Charadrius dubius), and parrot bill (Paradoxornis webbiana), collected in and around Lake Shihwa, Korea, which receives wastewaters from an adjacent industrial complex. Mean concentrations of perfluorooctanesulfonate (PFOS) ranged from 185 to 314 ng/g ww and were similar to those reported for bird eggs from other urban areas. Long-chain perfluorocarboxylic acids (PFCAs) were also found in egg yolks often at great concentrations. Mean concentrations of perfluoroundecanoic acid (PFUnA) ranged from 95 to 201 ng/g ww. Perfluorooctanoic acid was detected in 32 of 44 egg samples, but concentrations were 100-fold less than those of PFOS. Relative concentrations of PFAs in all three species were similar with the predominance of PFOS (45-50%). There was a statistically significant correlation between PFUnA and perfluorodecanoic acid in egg yolks (p < 0.05), suggesting a common source of PFCAs. Using measured egg concentrations and diet concentrations, the ecological risk of the PFOS and PFA mixture to birds in Lake Shihwa was evaluated using two different approaches. Estimated hazard quotients were similar between the two approaches. The concentration of PFOS associated with 90th centile in bird eggs was 100-fold less than the lowest observable adverse effect level determined for birds, and those concentrations were 4-fold less than the suggested toxicity reference values. On the basis of limited toxicological data, current concentrations of PFOS are less than what would be expected to have an adverse effect on birds in the Lake Shihwa region.

  7. Craters Without Ejecta

    NASA Technical Reports Server (NTRS)

    Housen, Kevin R.; Holsapple, Keith A.

    2012-01-01

    A significant portion of the Solar System's population of minor bodies may be quite porous. A unique aspect of crater formation in porous bodies is that large craters may form without the ejecta deposits that are associated with craters on less porous bodies. In this paper. laboratory experiments and scaling theories are used to identify the conditions under which ejecta deposits are suppressed. The results are consistent with the interpretation that large craters on asteroid Mathilde (porosity approx. 50%) and Saturn's moon Hyperion (porosity >40%) apparently formed without producing Significant ejecta deposits. while smaller bodies do have notable regoliths.

  8. Venus - Stein Triplet Crater

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The Magellan synthetic aperture radar (SAR) imaged this unique 'triplet crater,' or 'crater field' during orbits 418-421 on 21 September 1990. These craters are 14 kilometers, 11 kilometers, and 9 kilometers in diameter, respectively, and are centered at latitude -30.1 degrees south and longitude 345.5 degrees east. The Magellan Science Team has proposed the name Stein for this crater field after the American author, Gertrude Stein. This name has not yet been approved by the International Astronomical Union. The crater field was formed on highly fractured plains. The impacts generated a considerable amount of low viscosity 'flows' thought to consist largely of shock-melted target material along with fragmented debris from the crater. The three craters appear to have relatively steep walls based on the distortion in the image of the near and far walls of the craters in the Magellan radar look direction (from the left). The flow deposits from the three craters extend dominantly to the northeast (upper right).

  9. Cratering reservoir potential by impact cratering

    SciTech Connect

    Schultz, P.H.

    1996-12-31

    Impact craters are gaining increasing acceptance and value as sites for potential hydrocarbon reservoirs. Nevertheless, such structures are often difficult to interpret and assess because their physical expressions from physical data have few exposed terrestrial analogs for comparison. Observational, theoretical, and experimental studies directed - toward understanding the nature of well-preserved craters on other planets, however, establish a two-dimensional template for understanding and interpreting the three-dimensional view, critical or assessing hydrocarbon potentials. But terminology often used in describing an impact structure needs to be placed in a process context. Impact craters are not produced instantaneously but evolve through time. The process occurs in three different stages of formation corresponding to the transfer of kinetic energy: compression, excavation, and modification. The compression stage roughly corresponds to the time required for transfer of energy from impactor to target and is reflected in the formation of a central penetration zone in smaller craters and the central uplift in larger craters often called the {open_quotes}central plug, diapir, brecciated core, or distributed zone{close_quotes}. The excavation stage occurs as the cratering flow field draws material downward near the center and outward from the cavity. Traps are created stratigraphically inside (shock-disrupted rock and depositional capping) or outside (inverted stratigraphy, fractured/fault target, porous ejecta) as well as structurally inside (uplift, wall terraces) or outside (concentric listric faults or seismically triggered failure). Larger complex craters create greater potential traps. Consequently, potential reserve can be created during each stage but the most important criteria remains the realtors motto: location, location, location!

  10. Cratering reservoir potential by impact cratering

    SciTech Connect

    Schultz, P.H. )

    1996-01-01

    Impact craters are gaining increasing acceptance and value as sites for potential hydrocarbon reservoirs. Nevertheless, such structures are often difficult to interpret and assess because their physical expressions from physical data have few exposed terrestrial analogs for comparison. Observational, theoretical, and experimental studies directed - toward understanding the nature of well-preserved craters on other planets, however, establish a two-dimensional template for understanding and interpreting the three-dimensional view, critical or assessing hydrocarbon potentials. But terminology often used in describing an impact structure needs to be placed in a process context. Impact craters are not produced instantaneously but evolve through time. The process occurs in three different stages of formation corresponding to the transfer of kinetic energy: compression, excavation, and modification. The compression stage roughly corresponds to the time required for transfer of energy from impactor to target and is reflected in the formation of a central penetration zone in smaller craters and the central uplift in larger craters often called the [open quotes]central plug, diapir, brecciated core, or distributed zone[close quotes]. The excavation stage occurs as the cratering flow field draws material downward near the center and outward from the cavity. Traps are created stratigraphically inside (shock-disrupted rock and depositional capping) or outside (inverted stratigraphy, fractured/fault target, porous ejecta) as well as structurally inside (uplift, wall terraces) or outside (concentric listric faults or seismically triggered failure). Larger complex craters create greater potential traps. Consequently, potential reserve can be created during each stage but the most important criteria remains the realtors motto: location, location, location

  11. The Hydrothermal System at Home Plate in Gusev Crater, Mars: Formation of High Silica Material by Acid-Sulfate Alteration of Basalt

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Ming, D. W.; Gellert, R.; Yen, A.; Clark, B. C.; Gnaff, T. G.; Arvidson, R. E.; Squyres, S. W.

    2008-01-01

    The Alpha Particle X-ray Spectrometer (APXS) instrument on the Mars Exploration Rover (MER) Spirit measured three targets on or adjacent to Home Plate in Gusev Crater that have unusually high SiO2 concentrations (68% to 91%), unusually low FeO concentrations (1% to 7%, with total Fe as FeO), and unusually high TiO2/FeO ratios (0.2 to 1.2 by weight) [1]. Two targets (Kenosha Comets and Lefty Ganote) are located on high albedo soil (Gertrude Weise) that was exposed by the rover wheels, and one target is a float rock called Fuzzy Smith. Kenosha Comets has the highest SiO2 concentration, lowest FeO concentration, and highest TiO2/FeO ratio. Mineralogical evidence from the MER Miniature Thermal Emission Spectrometer (Mini-TES) suggests that the SiO2 is present as amorphous (noncrystalline) SiO2 at Gertrude Weise and nearby targets [2,3]. Mini-TES data were not acquired for Fuzzy Smith. Home Plate is considered to have an explosive volcanic origin, resulting when basaltic magma came into contact with ground water or ice [4]. Within 50 m to 1 km of Home Plate are sulfate rich soil deposits (Paso Robles class soils with 22-35% SO3) which are considered to be probable fumarolic and/or hydrothermal deposits associated with the volcanism [5]. We develop the model here, suggested by [5], that the high-silica materials are another manifestation of acid-sulfate processes associated with fumarolic and hydrothermal activity at Home Plate. This is done by analogy with basaltic materials altered by acid sulfate processes on the Island of Hawaii.

  12. Common Loon (Gavia immer) eggshell thickness and egg volume vary with acidity of nest lake in northern Wisconsin

    USGS Publications Warehouse

    Pollentier, C.D.; Kenow, K.P.; Meyer, M.W.

    2007-01-01

    Environmental acidification has been associated with factors that may negatively affect reproduction in many waterbirds. Declines in lake pH can lead to reductions in food availability and quality, or result in the altered availability of toxic metals, such as mercury. A recent laboratory study conducted by the U.S. Geological Survey and the Wisconsin Department of Natural Resources indicated that Common Loon (Gavia immer) chicks hatched from eggs collected on acidic lakes in northern Wisconsin may be less responsive to stimuli and exhibit reduced growth compared to chicks from neutral-pH lakes. Here we report on the relation between Common Loon egg characteristics (eggshell thickness and egg volume) and lake pH, as well as eggshell methylmercury content. Eggs (N = 84) and lake pH measurements were obtained from a four county region of northern Wisconsin. Egg-shells were 3-4% thinner on lakes with pH ??? 6.3 than on neutral-pH lakes and this relation was linear across the pH range investigated (P 0.05, n.s.) or lake pH. Results suggest that low lake pH may be associated with thinner eggshells and reduced egg volume in Common Loons. We speculate on the mechanisms that may lead to this phenomeno.

  13. Buffer capacities of fresh water lakes sensitive to acid rain deposition

    SciTech Connect

    Faust, S.D.; McIntosh, A.

    1983-01-01

    The Van Slyke definition of buffer capacity, the increment of a strong base or strong acid that causes an incremental change in the pH value of water, is better than total alkalinity for defining a water's resistance to acid rain. This Van Slyke value, designated by beta, shows a peak at pH 6.3 for the bicarbonate-carbonate pair, indicating that the effect of acid rain on the pH and alkalinity of natural waters is not deleterious until this peak is traversed. A beta value of zero indicates a dead water with no capacity to neutralize acid. The beta values, pH and total alkalinity of lakes, reservoirs, and streams in New Jersey are given. Data clearly show that pH and alkalinity alone cannot determine buffer capacity. For example: Fairview Lake (pH of 5.5 and alkalinity of 10.2 mg per liter) has a beta value 11 times that of Clyde Potts Reservoir (pH of 7.3, alkalinity of 8.1 mg per liter). 3 references, 1 figure, 1 table.

  14. Stratigraphy, mineralogy, and origin of layered deposits inside Terby crater, Mars

    NASA Astrophysics Data System (ADS)

    Ansan, V.; Loizeau, D.; Mangold, N.; Le Mouélic, S.; Carter, J.; Poulet, F.; Dromart, G.; Lucas, A.; Bibring, J.-P.; Gendrin, A.; Gondet, B.; Langevin, Y.; Masson, Ph.; Murchie, S.; Mustard, J. F.; Neukum, G.

    2011-01-01

    The 174 km diameter Terby impact crater (28.0°S-74.1°E) located on the northern rim of the Hellas basin displays anomalous inner morphology, including a flat floor and light-toned layered deposits. An analysis of these deposits was performed using multiple datasets from Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter missions, with visible images for interpretation, near-infrared data for mineralogical mapping, and topography for geometry. The geometry of layered deposits was consistent with that of sediments that settled mainly in a sub-aqueous environment, during the Noachian period as determined by crater counts. To the north, the thickest sediments displayed sequences for fan deltas, as identified by 100 m to 1 km long clinoforms, as defined by horizontal beds passing to foreset beds dipping by 6-10° toward the center of the Terby crater. The identification of distinct sub-aqueous fan sequences, separated by unconformities and local wedges, showed the accumulation of sediments from prograding/onlapping depositional sequences, due to lake level and sediment supply variations. The mineralogy of several layers with hydrated minerals, including Fe/Mg phyllosilicates, supports this type of sedimentary environment. The volume of fan sediments was estimated as >5000 km 3 (a large amount considering classical martian fan deltas such as Eberswalde (6 km 3)) and requires sustained liquid water activity. Such a large sedimentary deposition in Terby crater is characteristic of the Noachian/Phyllosian period during which the environment favored the formation of phyllosilicates. The latter were detected by spectral data in the layered deposits of Terby crater in three distinct layer sequences. During the Hesperian period, the sediments experienced strong erosion, possibly enhanced by more acidic conditions, forming the current morphology with three mesas and closed depressions. Small fluvial valleys and alluvial fans formed subsequently

  15. Geochemical characterization of acid mine lakes in northwest Turkey and their effect on the environment.

    PubMed

    Yucel, Deniz Sanliyuksel; Baba, Alper

    2013-04-01

    Mining activity generates a large quantity of mine waste. The potential hazard of mine waste depends on the host mineral. The tendency of mine waste to produce acid mine drainage (AMD) containing potentially toxic metals depends on the amounts of sulfide, carbonate minerals, and trace-element concentrations found in ore deposits. The acid mine process is one of the most significant environmental challenges and a major source of water pollution worldwide. AMD and its effects were studied in northwest Turkey where there are several sedimentary and hydrothermal mineral deposits that have been economically extracted. The study area is located in Can county of Canakkale province. Canakkale contains marine, lagoon, and lake sediments precipitated with volcanoclastics that occurred as a result of volcanism, which was active during various periods from the Upper Eocene to Plio-Quaternary. Can county is rich in coal with a total lignite reserve >100 million tons and contains numerous mines that were operated by private companies and later abandoned without any remediation. As a result, human intervention in the natural structure and topography has resulted in large open pits and deterioration in these areas. Abandoned open pit mines typically fill with water from runoff and groundwater discharge, producing artificial lakes. Acid drainage waters from these mines have resulted in the degradation of surface-water quality around Can County. The average pH and electrical conductivity of acid mine lakes (AMLs) in this study were found to be 3.03 and 3831.33 μS cm(-1), respectively. Total iron (Fe) and aluminum (Al) levels were also found to be high (329.77 and 360.67 mg L(-1), respectively). The results show that the concentration of most elements, such as Fe and Al in particular, exceed national and international water-quality standards.

  16. Geochemical characterization of acid mine lakes in northwest Turkey and their effect on the environment.

    PubMed

    Yucel, Deniz Sanliyuksel; Baba, Alper

    2013-04-01

    Mining activity generates a large quantity of mine waste. The potential hazard of mine waste depends on the host mineral. The tendency of mine waste to produce acid mine drainage (AMD) containing potentially toxic metals depends on the amounts of sulfide, carbonate minerals, and trace-element concentrations found in ore deposits. The acid mine process is one of the most significant environmental challenges and a major source of water pollution worldwide. AMD and its effects were studied in northwest Turkey where there are several sedimentary and hydrothermal mineral deposits that have been economically extracted. The study area is located in Can county of Canakkale province. Canakkale contains marine, lagoon, and lake sediments precipitated with volcanoclastics that occurred as a result of volcanism, which was active during various periods from the Upper Eocene to Plio-Quaternary. Can county is rich in coal with a total lignite reserve >100 million tons and contains numerous mines that were operated by private companies and later abandoned without any remediation. As a result, human intervention in the natural structure and topography has resulted in large open pits and deterioration in these areas. Abandoned open pit mines typically fill with water from runoff and groundwater discharge, producing artificial lakes. Acid drainage waters from these mines have resulted in the degradation of surface-water quality around Can County. The average pH and electrical conductivity of acid mine lakes (AMLs) in this study were found to be 3.03 and 3831.33 μS cm(-1), respectively. Total iron (Fe) and aluminum (Al) levels were also found to be high (329.77 and 360.67 mg L(-1), respectively). The results show that the concentration of most elements, such as Fe and Al in particular, exceed national and international water-quality standards. PMID:23223936

  17. Development of a total maximum daily load (TMDL) for acid-impaired lakes in the Adirondack region of New York

    NASA Astrophysics Data System (ADS)

    Fakhraei, Habibollah; Driscoll, Charles T.; Selvendiran, Pranesh; DePinto, Joseph V.; Bloomfield, Jay; Quinn, Scott; Rowell, H. Chandler

    2014-10-01

    Acidic deposition has impaired acid-sensitive surface waters in the Adirondack region of New York by decreasing pH and acid neutralizing capacity (ANC). In spite of air quality programs over past decades, 128 lakes in the Adirondacks were classified as “impaired” under Section 303(d) of the Clean Water Act in 2010 due to elevated acidity. The biogeochemical model, PnET-BGC, was used to relate decreases in atmospheric sulfur (S) and nitrogen (N) deposition to changes in lake water chemistry. The model was calibrated and confirmed using observed soil and lake water chemistry data and then was applied to calculate the maximum atmospheric deposition that the impaired lakes can receive while still achieving ANC targets. Two targets of ANC were used to characterize the recovery of acid-impaired lakes: 11 and 20 μeq L-1. Of the 128 acid-impaired lakes, 97 currently have ANC values below the target value of 20 μeq L-1 and 83 are below 11 μeq L-1. This study indicates that a moderate control scenario (i.e., 60% decrease from the current atmospheric S load) is projected to recover the ANC of lakes at a mean rate of 0.18 and 0.05 μeq L-1 yr-1 during the periods 2022-2050 and 2050-2200, respectively. The total maximum daily load (TMDL) of acidity corresponding to this moderate control scenario was estimated to be 7.9 meq S m-2 yr-1 which includes a 10% margin of safety.

  18. Spatial characterization of acid rain stress in Canadian Shield Lakes. Progress report, 1 August 1986-1 February 1987

    SciTech Connect

    Tanis, F.J.

    1987-01-01

    The acidification of lake waters from airborne pollution is of continental proportions both in North America and Europe. A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forest. The number of lakes affected in northeastern U.S. and on the Canadian Shield is though to be enormous. How seasonal changes in lake transparency are related to annual acidic load was examined. The relationship between variations in lake acidification and ecophysical units was also examined. The utility of Thematic Mapper based observations to measure seasonal changes in the optical transparency in acid lakes was investigated. The potential for this optical response is related to a number of local ecophysical factors with bedrock geology being, perhaps, the most important. Other factors include sulfate deposition, vegetative cover, and terrain drainage/relief. The area of southern Ontario contains a wide variety of geologies from the most acid rain sensitive granite quartzite types to the least sensitive limestone dolomite sediments. Annual sulfate deposition ranges from 1.0 to 4.0 grams/sq m.

  19. 'Endurance Crater' Overview

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This overview of 'Endurance Crater' traces the path of the Mars Exploration Rover Opportunity from sol 94 (April 29, 2004) to sol 205 (August 21, 2004). The route charted to enter the crater was a bit circuitous, but well worth the extra care engineers took to ensure the rover's safety. On sol 94, Opportunity sat on the edge of this impressive, football field-sized crater while rover team members assessed the scene. After traversing around the 'Karatepe' region and past 'Burns Cliff,' the rover engineering team assessed the possibility of entering the crater. Careful analysis of the angles Opportunity would face, including testing an Earth-bound model on simulated martian terrain, led the team to decide against entering the crater at that particular place. Opportunity then backed up before finally dipping into the crater on its 130th sol (June 5, 2004). The rover has since made its way down the crater's inner slope, grinding, trenching and examining fascinating rocks and soil targets along the way. The rover nearly made it to the intriguing dunes at the bottom of the crater, but when it got close, the terrain did not look safe enough to cross.

  20. Chemical, crystallographic and stable isotopic properties of alunite and jarosite from acid-Hypersaline Australian lakes

    USGS Publications Warehouse

    Alpers, C.N.; Rye, R.O.; Nordstrom, D.K.; White, L.D.; King, B.-S.

    1992-01-01

    Chemical, crystallographic and isotopic analyses were made on samples containing alunite and jarosite from the sediments of four acid, hypersaline lakes in southeastern and southwestern Australia. The alunite and jarosite are K-rich with relatively low Na contents based on chemical analysis and determination of unit cell dimensions by powder X-ray diffraction. Correcting the chemical analyses of fine-grained mineral concentrates from Lake Tyrrell, Victoria, for the presence of halite, silica and poorly crystalline aluminosilicates, the following formulas indicate best estimates for solid-solution compositions: for alunite, K0.87Na0.04(H3O)0.09(Al 0.92Fe0.08)3(SO4)2(OH) 6 and for jarosite, K0.89Na0.07(H3O)0.04(Fe 0.80Al0.20)3(SO4)2(OH) 6. The ??D-values of alunite are notably larger than those for jarosite from Lake Tyrrell and it appears that the minerals have closely approached hydrogen isotope equilibrium with the acidic regional groundwaters. The ??D results are consistent with a fractionation ???60-70??? between alunite and jarosite observed in other areas. However, interpretation of ??D results is complicated by large variability in fluid ??DH2O from evaporation, mixing and possible ion hydration effects in the brine. ??D-values of water derived from jarosite by step-wise heating tend to be smaller at 250??C, at which temperature hydronium and other non-hydroxyl water is liberated, than at 550??C, where water is derived from the hydroxyl site, but the differences are not sufficiently different to invalidate measurements of total ??D obtained by conventional, single-step heating methods. ??34S-values for alunite and jarosite from the four lakes (+19.7 to +21.2??? CDT) and for aqueous sulfate from Lake Tyrrell (+18.3 to +19.8???) are close to the values for modern evaporites (+21.5 ??0.3???) and seawater (+20??0.5???) and are probably typical of seawater-derived aerosols in arid coastal environments. ??34-S-values slightly smaller than that for seawater may

  1. Centrifuge Impact Cratering Experiments

    NASA Technical Reports Server (NTRS)

    Schmidt, R. M.; Housen, K. R.; Bjorkman, M. D.

    1985-01-01

    The kinematics of crater growth, impact induced target flow fields and the generation of impact melt were determined. The feasibility of using scaling relationships for impact melt and crater dimensions to determine impactor size and velocity was studied. It is concluded that a coupling parameter determines both the quantity of melt and the crater dimensions for impact velocities greater than 10km/s. As a result impactor radius, a, or velocity, U cannot be determined individually, but only as a product in the form of a coupling parameter, delta U micron. The melt volume and crater volume scaling relations were applied to Brent crater. The transport of melt and the validity of the melt volume scaling relations are examined.

  2. Exhuming South Polar Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    7 February 2004 The large, circular feature in this image is an old meteor impact crater. The crater is larger than the 3 kilometers-wide (1.9 miles-wide) Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, thus only part of the crater is seen. The bright mesas full of pits and holes--in some areas resembling swiss cheese--are composed of frozen carbon dioxide. In this summertime view, the mesa slopes and pit walls are darkened as sunlight causes some of the ice to sublime away. At one time in the past, the crater shown here may have been completely covered with carbon dioxide ice, but, over time, it has been exhumed as the ice sublimes a little bit more each summer. The crater is located near 86.8oS, 111.6oW. Sunlight illuminates this scene from the upper left.

  3. Buried Craters of Utopia

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-365, 19 May 2003

    Beneath the northern plains of Mars are numerous buried meteor impact craters. One of the most heavily-cratered areas, although buried, occurs in Utopia Planitia, as shown in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The history of Mars is complex; impact craters provide a tool by which to understand some of that history. In this case, a very ancient, cratered surface was thinly-buried by younger material that is not cratered at all. This area is near 48.1oN, 228.2oW; less than 180 km (112 mi) west of the Viking 2 lander site. Sunlight illuminates the scene from the lower left.

  4. A history of the Lonar crater, India: An overview

    NASA Technical Reports Server (NTRS)

    Nayak, V. K.

    1992-01-01

    The origin of the circular structure at Lonar, India, described variously as cauldron, pit, hollow, depression, and crater, has been a controversial subject since the early nineteenth century. A history of its origin and other aspects from 1823 to 1990 are overviewed. The structure in the Deccan Trap Basalt is nearly circular with a breach in the northeast, 1830 m in diameter, 150 m deep, with a saline lake in the crater floor. Over the years, the origin of the Lonar structure has risen from volcanism, subsidence, and cryptovolcanism to an authentic meteorite impact crater. Lonar is unique because it is probably the only terrestrial crater in basalt and is the closest analog with the Moon's craters. Some unresolved questions are suggested. The proposal is made that the young Lonar impact crater, which is less than 50,000 years old, should be considered as the best crater laboratory analogous to those of the Moon, be treated as a global monument, and preserved for scientists to comprehend more about the mysteries of nature and impact cratering, which is now emerging as a fundamental ubiquitous geological process in the evolution of the planets.

  5. Organic matter preservation in the sediment of an acidic mining lake.

    PubMed

    Laskov, Christine; Amelung, Wulf; Peiffer, Stefan

    2002-10-15

    Sustainable management of acidic mining lakes requires knowledge on the origin and reactivity of its sedimentary organic matter. We identified different pools of organic matter (OM) in the Fe-rich sediment (up to 35 wt %) of an acidic (pH 2.8) mining lake using delta13C-signals, C/N ratios, and the markers alkanes, lignin-derived phenols, and benzenepolycarboxylic acids (BPCA). Additionally, a density fractionation was applied to each sediment layer. Three fractions, aquatic (AOM), terrestrial (TOM), and lignite-derived (LOM) organic matter, were discriminated, of which AOM comprises only a small fraction, with a minimum at the sediment bottom. The terrestrial contribution to sedimentary OM is higher than that of AOM but still low throughout the sediment core, whereas lignite-derived OM constitutes the major C-fraction, even in the upper sediment layers. The size of the carbon pools was quantified with a mass-balance approach, in which the BPCA content was utilized as an estimate for the lignite fraction in combination with the delta13C-signals of the three C fractions. The largest amount of OM was found in the heaviest (>2.4 g cm3) of the three density fractions of the two upper sediment layers, which implies strong interaction with iron hydroxides. Comparisons with C-oxidation rates revealed that besides the refractory origin of the OM, sorptive preservation by solid iron phases controls C-reactivity in the sediment and, hence, the internal neutralization capacity of the lake system.

  6. Impact Crater with Peak

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 14 June 2002) The Science This THEMIS visible image shows a classic example of a martian impact crater with a central peak. Central peaks are common in large, fresh craters on both Mars and the Moon. This peak formed during the extremely high-energy impact cratering event. In many martian craters the central peak has been either eroded or buried by later sedimentary processes, so the presence of a peak in this crater indicates that the crater is relatively young and has experienced little degradation. Observations of large craters on the Earth and the Moon, as well as computer modeling of the impact process, show that the central peak contains material brought from deep beneath the surface. The material exposed in these peaks will provide an excellent opportunity to study the composition of the martian interior using THEMIS multi-spectral infrared observations. The ejecta material around the crater can is well preserved, again indicating relatively little modification of this landform since its initial creation. The inner walls of this approximately 18 km diameter crater show complex slumping that likely occurred during the impact event. Since that time there has been some downslope movement of material to form the small chutes and gullies that can be seen on the inner crater wall. Small (50-100 m) mega-ripples composed of mobile material can be seen on the floor of the crater. Much of this material may have come from the walls of the crater itself, or may have been blown into the crater by the wind. The Story When a meteor smacked into the surface of Mars with extremely high energy, pow! Not only did it punch an 11-mile-wide crater in the smoother terrain, it created a central peak in the middle of the crater. This peak forms kind of on the 'rebound.' You can see this same effect if you drop a single drop of milk into a glass of milk. With craters, in the heat and fury of the impact, some of the land material can even liquefy. Central peaks like the one

  7. Venus - Mead Crater

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This Magellan image mosaic shows the largest (275 kilometers in diameter [170 miles]) impact crater known to exist on Venus at this point in the Magellan mission. The crater is located north of Aphrodite Terra and east of Eistla Regio at latitude 12.5 degrees north and longitude 57.4 degrees east, and was imaged during Magellan orbit 804 on November 12, 1990. The Magellan science team has proposed to name this crater Mead, after Margaret Mead, the American Anthropologist (1901- 1978). All Magellan-based names of features on Venus are, of course, only proposed until final approval is given by the International Astronomical Union-Commission on Planetary Nomenclature. Mead is classified as a multi-ring crater with its innermost, concentric scarp being interpreted as the rim of the original crater cavity. No inner peak-ring of mountain massifs is observed on Mead. The presence of hummocky, radar-bright crater ejecta crossing the radar-dark floor terrace and adjacent outer rim scarp suggests that the floor terrace is probably a giant rotated block that is concentric to, but lies outside of, the original crater cavity. The flat, somewhat brighter inner floor of Mead is interpreted to result from considerable infilling of the original crater cavity by impact melt and/or by volcanic lavas. To the southeast of the crater rim, emplacement of hummocky ejecta appears to have been impeded by the topography of preexisting ridges, thus suggesting a very low ground-hugging mode of deposition for this material. Radar illumination on this and all other Magellan image products is from the left to the right in the scene.

  8. Craters on comets

    NASA Astrophysics Data System (ADS)

    Vincent, Jean-Baptiste; Oklay, Nilda; Marchi, Simone; Höfner, Sebastian; Sierks, Holger

    2015-03-01

    This paper reviews the observations of crater-like features on cometary nuclei. We compare potential crater sizes and morphologies, and we discuss the probability of impacts between small asteroids in the Main Belt and a comet crossing this region of the Solar System. Finally, we investigate the fate of the impactor and its chances of survival on the nucleus. We find that comets do undergo impacts although the rapid evolution of the surface erases most of the features and make craters difficult to detect. In the case of a collision between a rocky body and a highly porous cometary nucleus, two specific crater morphologies can be formed: a central pit surrounded by a shallow depression, or a pit, deeper than typical craters observed on rocky surfaces. After the impact, it is likely that a significant fraction of the projectile will remain in the crater. During its two years long escort of comet 67P/Churyumov-Gerasimenko, ESA's mission Rosetta should be able to detect specific silicates signatures at the bottom of craters or crater-like features, as evidence of this contamination. For large craters, structural changes in the impacted region, in particular compaction of material, will affect the local activity. The increase of tensile strength can extinct the activity by preventing the gas from lifting up dust grains. On the other hand, material compaction can help the heat flux to travel deeper in the nucleus, potentially reaching unexposed pockets of volatiles, and therefore increasing the activity. Ground truth data from Rosetta will help us infer the relative importance of those two effects.

  9. Prolonged Ponding Episode in C-Newton Crater in Recent Geological Times on Mars

    NASA Technical Reports Server (NTRS)

    Grin, E. A.; Cabrol, N. A.; Wynn-Williams, D. D.

    2001-01-01

    We present the morphological evidence that supports the existence of a lake in a recent past in C-Newton crater. We assess the astrobiological potential of this environment. Additional information is contained in the original extended abstract.

  10. Venus - Crater Aurelia

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This Magellan image shows a complex crater, 31.9 kilometers (20 miles) in diameter with a circular rim, terraced walls, and central peaks, located at 20.3 degrees north latitude and 331.8 degrees east longitude. Several unusual features are evidenced in this image: large dark surface up range from the crater; lobate flows emanating from crater ejecta, and very radar-bright ejecta and floor. Aurelia has been proposed to the International Astronomical Union, Subcommittee of Planetary Nomenclature as a candidate name. Aurelia is the mother of Julius Caesar.

  11. Crater in Utopia

    NASA Technical Reports Server (NTRS)

    2004-01-01

    23 March 2004 Craters of the martian northern plains tend to be somewhat shallow because material has filled them in. Their ejecta blankets, too, are often covered by younger materials. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example--a crater in Utopia Planitia near 43.7oN, 227.3oW. Erosion has roughened some of the surfaces of the material that filled the crater and covered its ejecta deposit. The picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  12. One View, Two Craters

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This cylindrical projection was constructed from a sequence of four images taken by the navigation camera onboard the Mars Exploration Rover Opportunity.

    The images were acquired on sol 85 of Opportunity's mission to Meridiani Planum. The camera acquired the images at approximately 14:28 local solar time, or around 6:30 a.m. Pacific Daylight Time, on April 20, 2004.

    The view is from the rover's new location, a region dubbed 'Fram Crater' located some 450 meters (.3 miles) from 'Eagle Crater' and roughly 250 meters (820 feet) from 'Endurance Crater' (upper right).

  13. Pre-industrial atmospheric pollution: was it important for the pH of acid-sensitive Swedish lakes?

    PubMed

    Bindler, Richard; Korsman, Tom; Renberg, Ingemar; Högberg, Peter

    2002-09-01

    Acid rain has caused extensive surface water acidification in Sweden since the mid-20th century. Sulfur emissions from fossil-fuel burning and metal production were the main sources of acid deposition. In the public consciousness, acid deposition is strongly associated with the industrial period, in particular the last 50 years. However, studies of lake-water pH development and atmospheric pollution, based on analyses of lake sediment deposits, have shown the importance of a long-term perspective. Here, we present a conceptual argument, using the sediment record, that large-scale atmospheric acid deposition has impacted the environment since at least Medieval times. Sulfur sources were the pre-industrial mining and metal industries that produced silver, lead and other metals from sulfide ores. This early excess sulfur deposition in southern Sweden did not cause surface water acidification; on the contrary, it contributed to alkalization, i.e. increased pH and productivity of the lakes. Suggested mechanisms are that the excess sulfur caused enhanced cation exchange in catchment soils, and that it altered iron-phosphorus cycling in the lakes, which released phosphorus and increased lake productivity.

  14. Assessment of factors limiting algal growth in acidic pit lakes--a case study from Western Australia, Australia.

    PubMed

    Kumar, R Naresh; McCullough, Clint D; Lund, Mark A; Larranaga, Santiago A

    2016-03-01

    Open-cut mining operations can form pit lakes on mine closure. These new water bodies typically have low nutrient concentrations and may have acidic and metal-contaminated waters from acid mine drainage (AMD) causing low algal biomass and algal biodiversity. A preliminary study was carried out on an acidic coal pit lake, Lake Kepwari, in Western Australia to determine which factors limited algal biomass. Water quality was monitored to obtain baseline data. pH ranged between 3.7 and 4.1, and solute concentrations were slightly elevated to levels of brackish water. Concentrations of N were highly relative to natural lakes, although concentrations of FRP (<0.01 mg/L) and C (total C 0.7-3.7 and DOC 0.7-3.5 mg/L) were very low, and as a result, algal growth was also extremely low. Microcosm experiment was conducted to test the hypothesis that nutrient enrichment will be able to stimulate algal growth regardless of water quality. Microcosms of Lake Kepwari water were amended with N, P and C nutrients with and without sediment. Nutrient amendments under microcosm conditions could not show any significant phytoplankton growth but was able to promote benthic algal growth. P amendments without sediment showed a statistically higher mean algal biomass concentration than controls or microcosms amended with phosphorus but with sediment did. Results indicated that algal biomass in acidic pit lake (Lake Kepwari) may be limited primarily by low nutrient concentrations (especially phosphorus) and not by low pH or elevated metal concentrations. Furthermore, sediment processes may also reduce the nutrient availability. PMID:26593729

  15. Assessment of factors limiting algal growth in acidic pit lakes--a case study from Western Australia, Australia.

    PubMed

    Kumar, R Naresh; McCullough, Clint D; Lund, Mark A; Larranaga, Santiago A

    2016-03-01

    Open-cut mining operations can form pit lakes on mine closure. These new water bodies typically have low nutrient concentrations and may have acidic and metal-contaminated waters from acid mine drainage (AMD) causing low algal biomass and algal biodiversity. A preliminary study was carried out on an acidic coal pit lake, Lake Kepwari, in Western Australia to determine which factors limited algal biomass. Water quality was monitored to obtain baseline data. pH ranged between 3.7 and 4.1, and solute concentrations were slightly elevated to levels of brackish water. Concentrations of N were highly relative to natural lakes, although concentrations of FRP (<0.01 mg/L) and C (total C 0.7-3.7 and DOC 0.7-3.5 mg/L) were very low, and as a result, algal growth was also extremely low. Microcosm experiment was conducted to test the hypothesis that nutrient enrichment will be able to stimulate algal growth regardless of water quality. Microcosms of Lake Kepwari water were amended with N, P and C nutrients with and without sediment. Nutrient amendments under microcosm conditions could not show any significant phytoplankton growth but was able to promote benthic algal growth. P amendments without sediment showed a statistically higher mean algal biomass concentration than controls or microcosms amended with phosphorus but with sediment did. Results indicated that algal biomass in acidic pit lake (Lake Kepwari) may be limited primarily by low nutrient concentrations (especially phosphorus) and not by low pH or elevated metal concentrations. Furthermore, sediment processes may also reduce the nutrient availability.

  16. The complex filling of alae crater, Kilauea Volcano, Hawaii

    USGS Publications Warehouse

    Swanson, D.A.; Duffield, W.A.; Jackson, D.B.; Peterson, D.W.

    1972-01-01

    Since February 1969 Alae Crater, a 165-m-deep pit crater on the east rift of Kilauea Volcano, has been completely filled with about 18 million m3 of lava. The filling was episodic and complex. It involved 13 major periods of addition of lava to the crater, including spectacular lava falls as high as 100 m, and three major periods of draining of lava from the crater. Alae was nearly filled by August 3, 1969, largely drained during a violent ground-cracking event on August 4, 1969, and then filled to the low point on its rim on October 10, 1969. From August 1970 to May 1971, the crater acted as a reservoir for lava that entered through subsurface tubes leading from the vent fissure 150 m away. Another tube system drained the crater and carried lava as far as the sea, 11 km to the south. Much of the lava entered Alae by invading the lava lake beneath its crust and buoying the crust upward. This process, together with the overall complexity of the filling, results in a highly complicated lava lake that would doubtless be misinterpreted if found in the fossil record. ?? 1972 Stabilimento Tipografico Francesco Giannini & Figli.

  17. Craters in the Classroom.

    ERIC Educational Resources Information Center

    McArdle, Heather K.

    1997-01-01

    Details an activity in which students create and study miniature impact craters in the classroom. Engages students in making detailed, meaningful observations, drawing inferences, reaching conclusions based on scientific evidence, and designing experiments to test selected variables. (DDR)

  18. Fresh, Rayed Impact Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-416, 9 July 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a fresh, young meteor impact crater on the martian surface. It is less than 400 meters (less than 400 yards) across. While there is no way to know the exact age of this or any other martian surface feature, the rays are very well preserved. On a planet where wind can modify surface features at the present time, a crater with rayed ejecta patterns must be very young indeed. Despite its apparent youth, the crater could still be many hundreds of thousands, if not several million, of years old. This impact scar is located within the much larger Crommelin Crater, near 5.6oN, 10.0oW. Sunlight illuminates the scene from the left.

  19. Shackleton Crater Illumination

    NASA Video Gallery

    Simulated illumination conditions near the lunar South Pole. The 30km x 30km region highlights the Shackleton crater. The movie runs for 28 days, centered on the LCROSS impact date on October 9th, ...

  20. Clouds Near Mie Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-572, 12 December 2003

    Mie Crater, a large basin formed by asteroid or comet impact in Utopia Planitia, lies at the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red wide angle image. The crater is approximately 104 km (65 mi) across. To the east and southeast (toward the lower right) of Mie, in this 5 December 2003 view, are clouds of dust and water ice kicked up by local dust storm activity. It is mid-winter in the northern hemisphere of Mars, a time when passing storms are common on the northern plains of the red planet. Sunlight illuminates this image from the lower left; Mie Crater is located at 48.5oN, 220.3oW. Viking 2 landed west/southwest of Mie Crater, off the left edge of this image, in September 1976.

  1. Zhamanshin meteor crater

    NASA Technical Reports Server (NTRS)

    Florenskiy, P. V.; Dabizha, A. I.

    1987-01-01

    A historical survey and geographic, geologic and geophysical characteristics, the results of many years of study of the Zhamanshin meteor crater in the Northern Aral region, are reported. From this data the likely initial configuration and cause of formation of the crater are reconstructed. Petrographic and mineralogical analyses are given of the brecciated and remelted rocks, of the zhamanshinites and irgizite tektites in particular. The impact melting, dispersion and quenching processes resulting in tektite formation are discussed.

  2. Har Crater on Callisto

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image shows a heavily cratered region near Callisto's equator. It was taken by the Galileo spacecraft Solid State Imaging (CCD) system on its ninth orbit around Jupiter. North is to the top of the image. The 50 kilometer (30 mile) double ring crater in the center of the image is named Har. Har displays an unusual rounded mound on its floor. The origin of the mound is unclear but probably involves uplift of ice-rich materials from below, either as a 'rebound' immediately following the impact that formed the crater or as a later process. Har is older than the prominent 20 kilometer (12 mile) crater superposed on its western rim. The large crater partially visible in the northeast corner of the image is called Tindr. Chains of secondary craters (craters formed from the impact of materials thrown out of the main crater during an impact) originating from Tindr crosscut the eastern rim of Har.

    The image, centered at 3.3 degrees south latitude and 357.9 degrees west longitude, covers an area of 120 kilometers by 115 kilometers (75 miles by 70 miles). The sun illuminates the scene from the west (left). The smallest distinguishable features in the image are about 294 meters (973 feet) across. This image was obtained on June 25, 1997, when Galileo was 14,080 kilometers (8,590 miles) from Callisto.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  3. Named Venusian craters

    NASA Astrophysics Data System (ADS)

    Russell, Joel F.; Schaber, Gerald G.

    1993-03-01

    Schaber et al. compiled a database of 841 craters on Venus, based on Magellan coverage of 89 percent of the planet's surface. That database, derived from coverage of approximately 98 percent of Venus' surface, has been expanded to 912 craters, ranging in diameter from 1.5 to 280 km. About 150 of the larger craters were previously identified by Pioneer Venus and Soviet Venera projects and subsequently formally named by the International Astronomical Union (IAU). Altogether, the crater names submitted to the IAU for approval to date number about 550, a little more than half of the number of craters identified on Magellan images. The IAU will consider more names as they are submitted for approval. Anyone--planetary scientist or layman--may submit names; however, candidate names must conform to IAU rules. The person to be honored must be deceased for at least three years, must not be a religious figure or a military or political figure of the 19th or 20th century, and, for Venus, must be a woman. All formally and provisionally approved names for Venusian impact craters, along with their latitude, longitude, size, and origin of their name, will be presented at LPSC and will be available as handouts.

  4. High Elevation Lakes of the Western US: Are we Studying Systems Recovering from Excess Atmospheric Deposition of Acids and Nutrients?

    NASA Astrophysics Data System (ADS)

    Sickman, J. O.

    2011-12-01

    Instrumental records and monitoring of high elevation lakes began in most areas of the western US in the early 1980s. Much effort has been devoted to detecting changes in these aquatic ecosystems resulting from increased atmospheric deposition of acids and nutrients. However, there is growing evidence that thresholds for atmospheric pollutants were crossed much earlier in the 20th Century and that some of the subsequent hydrochemical and ecological changes observed in these lakes may be the result of recovery from earlier atmospheric forcing. We examine responses of high elevation lakes to atmospheric deposition on annual to century timescales using data from a 29-year study of Emerald Lake (Sequoia National Park) and paleolimnological analyses of other high elevation lakes incorporating diatom species analyses and geochemical proxies for fossil-fuel burning. At Emerald Lake, we have observed multiple transitions between nitrogen and phosphorus limitation of phytoplankton, the earliest of which occurred in the beginning of the 1980s and may be the result of reduction in N deposition due to the Clean Air Act. Critical loads analyses incorporating diatom species in lake sediments suggest that thresholds for N deposition were crossed in the period of 1950-1980 in the Rocky Mountains and likely much earlier, 1900-1920, in the Sierra Nevada. Diatom species composition is strongly controlled by acid neutralizing capacity (ANC) in the Sierra Nevada and we have observed a pronounced decline and recovery of ANC over the period of 1920-1980 in some Sierra Nevada lakes that coincides with the abundance of spheroidal carbonaceous particles (i.e., a diagnostic tracer of fossil fuel combustion) preserved in lake sediments; these patterns appear to be driven by increased emissions of oxidized N and S in the mid-20th Century and reductions in acid precursor levels caused by the Clean Air Act in the 1970s. Thus, when interpreting observational records from western high elevation

  5. Influence of bioturbation on the biogeochemistry of the sediment in the littoral zone of an acidic mine pit lake

    NASA Astrophysics Data System (ADS)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2010-10-01

    In the last decades, the mining exploitation of large areas in Lusatia (South-eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the oxygen consumption by sediment, and stimulated the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  6. Influence of bioturbation on the biogeochemistry of littoral sediments of an acidic post-mining pit lake

    NASA Astrophysics Data System (ADS)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2011-02-01

    In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  7. Enrichment of Non-Terrestrial L-Proteinogenic Amino Acids by Aqueous Alteration on the Tagish Lake Meteorite Parent Body

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Herd, Christopher D. K.

    2012-01-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography fluorescence detection time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approx. 43 to 59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha-hydrogen protein amino acid, was found to be nearly racemic (D approx. L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and D- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the Lexcesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals.

  8. Water chemistry of Lake Quilotoa (Ecuador) and assessment of natural hazards

    NASA Astrophysics Data System (ADS)

    Aguilera, E.; Chiodini, G.; Cioni, R.; Guidi, M.; Marini, L.; Raco, B.

    2000-04-01

    A geochemical survey carried out in November 1993 revealed that Lake Quilotoa was composed by a thin (˜14 m) oxic epilimnion overlying a ˜200 m-thick anoxic hypolimnion. Dissolved CO 2 concentrations reached 1000 mg/kg in the lower stratum. Loss of CO 2 from epilimnetic waters, followed by calcite precipitation and a consequent lowering in density, was the apparent cause of the stratification. The Cl, SO 4 and HCO 3 contents of Lake Quilotoa are intermediate between those of acid-SO 4-Cl Crater lakes and those of neutral-HCO 3 Crater lakes, indicating that Lake Quilotoa has a 'memory' of the inflow and absorption of HC1- and S-bearing volcanic (magmatic) gases. The Mg/Ca ratios of the lake waters are governed by dissolution of local volcanic rocks or magmas, but K/Na ratios were likely modified by precipitation of alunite, a typical mineral in acid-SO 4-Cl Crater lakes. The constant concentrations of several conservative chemical species from lake surface to lake bottom suggest that physical, chemical and biological processes did not have enough time, after the last overturn, to cause significant changes in the contents of these chemical species. This lapse of time might be relatively large, but it cannot be established on the basis of available data. Besides, the lake may not be close to steady state. Mixing of Lake Quilotoa waters could presently be triggered by either cooling epilimnetic waters by ˜4°C or providing heat to hypolimnetic waters or by seismic activity. Although Quilotoa lake contains a huge amount of dissolved CO 2(˜3×10 11 g), at present the risk of a dangerous limnic eruption seems to be nil even though some gas exsolution might occur if deep lake waters were brought to the surface. Carbon dioxide could build up to higher levels in deep waters than at present without any volcanic re-awakening, due to either a large inflow of relatively cool CO 2-rich gases, or possibly a long interval between overturns. Periodical geochemical surveys of

  9. Effects of Acid on Plant Litter Decomposition in an Arctic Lake

    PubMed Central

    McKinley, Vicky L.; Vestal, J. Robie

    1982-01-01

    The effects of acid on the microbial decomposition of the dominant aquatic macrophyte (Carex sp.) in Toolik Lake, Alaska were studied in microcosms during the ice-free season of 1980. Toolik Lake is slightly buffered, deep, and very oligotrophic. Microbial activities, as determined by 14C-acetate incorporation into extractable lipids, associated with Carex litter were significantly (P < 0.01) reduced within 2 days at pHs of 3.0 and 4.0, but not 5.0, 5.5, or 6.0, as compared with ambient controls (pH 7.4). ATP levels were significantly reduced at pH 3.0, but not at the other pHs tested. After 18 days, microbial activity significantly correlated with weight loss (P < 0.05), nitrogen content (P < 0.01), and C/N ratios (P < 0.01) of the litter, but did not correlate with ATP levels. Scanning electron microscopy of the litter surface revealed that the fungi present at ambient pH did not become dominant at pHs below 5.5, diatoms were absent below pH 4.0, and bacterial numbers and extracellular slime were greatly reduced at pH 4.0 and below. Mineralization of Carex14C-lignin-labeled or 14C-cellulose-labeled lignocellulose was reduced at pH 2.0, but not at pH 4.0, 5.0, or 6.0, compared with controls (pH 7). We concluded that if the pH of the water from this slightly buffered lake was sufficiently reduced, rates of litter decomposition would be significantly reduced. Images PMID:16346015

  10. Effects of acid on plant litter decomposition in an arctic lake. [Carex aquatilis

    SciTech Connect

    McKinley, V.L.; Vestal, J.R.

    1982-05-01

    The effects of acid on the microbial decomposition of the dominant aquatic macrophyte (Carex sp.) in Toolik Lake, Alaska were studied in microcosms during the ice-free season of 1980. Toolik Lake is slightly buffered, deep, and very oligotrophic. Microbial activities, as determined by /sup 14/C-acetate incorporation into extractable lipids, associated with Carex litter were signficantly (P < 0.01) reduced within 2 days at pHs of 3.0 and 4.0, but not 5.0, 5.5 or 6.0, as compared with ambient controls (pH 7.4). ATP levels were signficantly reduced at pH 3.0 but not at the other pHs tested. After 18 days, microbial activity signficantly correlated with weight loss (P < 0.05), nitrogen content (P < 0.01), and C/N ratios (P < 0.01) of the liter, but did not correlate with ATP levels. Scanning electron microscopy of the litter surface revealed that the fungi present at ambient pH did not become domimant at pHs below 5.5, diatoms were absent below pH 4.0, and bacterial numbers and extracellular slime were greatly reduced at pH 4.0 and below. Mineralization of Carex /sup 14/C-lignin-labeled or /sup 14/C-cellulose-labeled ligno-cellulose was reduced at pH 2.0, but not at pH 4.0, 5.0, or 6.0, compared with controls (pH '). We concluded that if the pH of the water from this slightly buffered lake was sufficiently reduced, rates of litter decomposition would be significantly reduced.

  11. Geology of McLaughlin Crater, Mars: A Unique Lacustrine Setting with Implications for Astrobiology

    NASA Technical Reports Server (NTRS)

    Michalski, J. R.; Niles, P. B.; Rogers, A. D.; Johnson, S. S.; Ashley, J. W.; Golombek, M. P.

    2016-01-01

    McLaughlin crater is a 92-kmdiameter Martian impact crater that contained an ancient carbonate- and clay mineral-bearing lake in the Late Noachian. Detailed analysis of the geology within this crater reveals a complex history with important implications for astrobiology [1]. The basin contains evidence for, among other deposits, hydrothermally altered rocks, delta deposits, deep water (>400 m) sediments, and potentially turbidites. The geology of this basin stands in stark contrast to that of some ancient basins that contain evidence for transient aqueous processes and airfall sediments (e.g. Gale Crater [2-3]).

  12. Impact Cratering Calculations

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.

    2002-01-01

    Many Martian craters are surrounded by ejecta blankets which appear to have been fluidized forming lobate and layered deposits terminated by one or more continuous distal scarps, or ramparts. One of the first hypotheses for the formation of so-called rampart ejecta features was shock-melting of subsurface ice, entrainment of liquid water into the ejecta blanket, and subsequent fluidized flow. Our work quantifies this concept. Rampart ejecta found on all but the youngest volcanic and polar regions, and the different rampart ejecta morphologies are correlated with crater size and terrain. In addition, the minimum diameter of craters with rampart features decreases with increasing latitude indicating that ice laden crust resides closer to the surface as one goes poleward on Mars. Our second goal in was to determine what strength model(s) reproduce the faults and complex features found in large scale gravity driven craters. Collapse features found in large scale craters require that the rock strength weaken as a result of the shock processing of rock and the later cratering shear flows. In addition to the presence of molten silicate in the intensely shocked region, the presence of water, either ambient, or the result of shock melting of ice weakens rock. There are several other mechanisms for the reduction of strength in geologic materials including dynamic tensile and shear induced fracturing. Fracturing is a mechanism for large reductions in strength. We found that by incorporating damage into the models that we could in a single integrated impact calculation, starting in the atmosphere produce final crater profiles having the major features found in the field measurements (central uplifts, inner ring, terracing and faulting). This was accomplished with undamaged surface strengths (0.1 GPa) and in depth strengths (1.0 GPa).

  13. Hydrogeochemical features of Lake Ngozi (SW Tanzania)

    NASA Astrophysics Data System (ADS)

    Delalande-Le Mouëllic, Manuëlla; Gherardi, Fabrizio; Williamson, David; Kajula, Stephen; Kraml, Michael; Noret, Aurélie; Abdallah, Issah; Mwandapile, Ezekiel; Massault, Marc; Majule, Amos; Bergonzini, Laurent

    2015-03-01

    Located on the triple rift junction hosting the Karonga-Usungu depression in Tanzania, Lake Ngozi is the second largest crater lake of the East African Rift. The lake has a number of peculiar features: it has a near constant water level, no permanent surface inlets and outlets, it is vertically well-mixed, with homogeneous distribution of temperature and chemical composition, and it is characterised by near neutral to slightly acid Na-Cl waters of comparatively high salinity and high P-CO2. Based on the different chemical signature of surface and ground waters (low-Cl type) from lake waters, mass balance methods have been applied to investigate lake dynamics. Water enters the lake mainly by precipitation and groundwater inflow, and leaves by groundwater outflow and evaporation. A large groundwater outflow of 2.4 m yr-1 has been estimated. The high salinity, Na-Cl signature of Lake Ngozi waters, together with 3He/4He ratios measured on dissolved gases (between 7 and 8.3 Ra) and high-PCO2 values estimated all along the water vertical column indicate the inflow of deep-seated fluids, likely magmatic in origin, into the lake. The existence of a hydrothermal system possibly at 250 °C in the root of the volcanic edifice is also hypothesised on the basis of solute geothermometry. Despite the current lack of vertical stratification, the lake is suspected to act as condenser for CO2 and other gases of deep magmatic origin, and should be then further monitored for the risk of limnic eruptions as well as for environmental and climatic concerns.

  14. Phytoplankton limitation by phosphorus and zooplankton grazing in an acidic Adirondack lake

    SciTech Connect

    Singer, R.; Evans, G.L.; Pratt, N.C.

    1984-08-01

    Lakes which are believed to have been acidified by atmospheric deposition of anthropogenic substances are known for their unusually high water clarity and low nutrient concentrations. Some evidence indicates that alterations in predator/prey relationships, an indirect effect of acidification, bring about the increase in water clarity. Enclosures were used to study the effects of phosphorus addition and zooplankton removal on the phytoplankton of an acidic lake in the Adirondack Mountains of New York. Fertilized enclosures had significantly lower alkalinities and contained significantly more dissolved oxygen after the incubation period than did unfertilized enclosures. The P concentration remained at or near the limit of detection in the unfertilized enclosures. The phytoplankton population bloomed after the addition of 80 micro g/liter of phosphate as KH/sub 2/PO/sub 4/. The response was measured by cell counts of the dominant phytoplankton. Chlamydomonas, and by changes in chlorophyll a concentration. About half the number of algal cells were present after the two week incubation when zooplankton were not removed, indicating that zooplankton herbivory can influence, but not totally control, the algal production. 46 references.

  15. Patterns in benthic biodiversity link lake trophic status to structure and potential function of three large, deep lakes.

    PubMed

    Hayford, Barbara L; Caires, Andrea M; Chandra, Sudeep; Girdner, Scott F

    2015-01-01

    Relative to their scarcity, large, deep lakes support a large proportion of the world's freshwater species. This biodiversity is threatened by human development and is in need of conservation. Direct comparison of biodiversity is the basis of biological monitoring for conservation but is difficult to conduct between large, insular ecosystems. The objective of our study was to conduct such a comparison of benthic biodiversity between three of the world's largest lakes: Lake Tahoe, USA; Lake Hövsgöl, Mongolia; and Crater Lake, USA. We examined biodiversity of common benthic organism, the non-biting midges (Chironomidae) and determined lake trophic status using chironomid-based lake typology, tested whether community structure was similar between the three lakes despite geographic distance; and tested whether chironomid diversity would show significant variation within and between lakes. Typology analysis indicated that Lake Hövsgöl was ultra-oligotrophic, Crater Lake was oligotrophic, and Lake Tahoe was borderline oligotrophic/mesotrophic. These results were similar to traditional pelagic measures of lake trophic status for Lake Hövsgöl and Crater Lake but differed for Lake Tahoe, which has been designated as ultra-oligotrophic by traditional pelagic measures such as transparency found in the literature. Analysis of similarity showed that Lake Tahoe and Lake Hövsgöl chironomid communities were more similar to each other than either was to Crater Lake communities. Diversity varied between the three lakes and spatially within each lake. This research shows that chironomid communities from these large lakes were sensitive to trophic conditions. Chironomid communities were similar between the deep environments of Lake Hövsgöl and Lake Tahoe, indicating that chironomid communities from these lakes may be useful in comparing trophic state changes in large lakes. Spatial variation in Lake Tahoe's diversity is indicative of differential response of chironomid

  16. Water-quality effects on Baker Lake of recent volcanic activity at Mount Baker, Washington

    USGS Publications Warehouse

    Bortleson, Gilbert Carl; Wilson, Reed T.; Foxworthy, B.L.

    1976-01-01

    Increased volcanic activity on Mount Baker, which began in March 1975, represents the greatest known activity of a Cascade Range volcano since eruptions at Lassen Peak, Calif. during 1914-17. Emissions of dust and increased emanations of steam, other gases, and heat from the Sherman Crater area of the mountain focused attention on the possibility of hazardous events, including lava flows, pyroclastic eruptions, avalanches, and mudflows. However, the greatest undesirable natural results that have been observed after one year of the increased activity are an increase in local atmospheric pollution and a decrease in the quality of some local water resources, including Baker Lake. Baker Lake, a hydropower reservoir behind Upper Baker Dam, supports a valuable fishery resource and also is used for recreation. The lake's feedwater is from Baker River and many smaller streams, some of which, like Boulder Creek, drain parts of Mount Baker. Boulder Creek receives water from Sherman Crater, and its channel is a likely route for avalanches or mudflows that might originate in the crater area. Boulder Creek drains only about 5 percent of the total drainage area of Baker Lake, but during 1975 carried sizeable but variable loads of acid and dissolved minerals into the lake. Sulfurous gases and the fumarole dust from Sherman Crater are the main sources for these materials, which are brought into upper Boulder Creek by meltwater from the crater. In September 1973, before the increased volcanic activity, Boulder Creek near the lake had a pH of 6.0-6.6; after the increase the pH ranged as low as about 3.5. Most nearby streams had pH values near 7. On April 29, in Boulder Creek the dissolved sulfate concentration was 6 to 29 times greater than in nearby creeks or in Baker River; total iron was 18-53 times greater than in nearby creeks; and other major dissolved constituents generally 2 to 7 times greater than in the other streams. The short-term effects on Baker Lake of the acidic

  17. Barringer Meteor Crater, Arizona

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Barringer Crater, also known as 'Meteor Crater,' is a 1,300-meter (0.8 mile) diameter, 174-meter (570-feet) deep hole in the flat-lying desert sandstones 30 kilometers (18.6 miles) west of Winslow, Arizona. Since the 1890s geologic studies here played a leading role in developing an understanding of impact processes on the Earth, the moon and elsewhere in the solar system.

    This view was acquired by the Landsat 4 satellite on December 14, 1982. It shows the crater much as a lunar crater might appear through a telescope. Morning sun illumination is from the southeast (lower right). The prominent gully meandering across the scene is known as Canyon Diablo. It drains northward toward the Little Colorado River and eventually to the Grand Canyon. The Interstate 40 highway crosses and nearly parallels the northern edge of the scene.

    The ejecta blanket around the crater appears somewhat lighter than the surrounding terrain, perhaps in part due to its altered mineralogic content. However, foot traffic at this interesting site may have scarred and lightened the terrain too. Also, the roughened surface here catches the sunlight on the southerly slopes and protects a highly reflective patchy snow cover in shaded northerly slopes, further lightening the terrain as viewed from space on this date.

  18. Decomposition of Alternative Chirality Amino Acids by Alkaliphilic Anaerobe from Owens Lake, California

    NASA Technical Reports Server (NTRS)

    Townsend, Alisa; Pikuta, Elena V.; Guisler, Melissa; Hoover, Richard B.

    2009-01-01

    The study of alkaliphilic microbial communities from anaerobic sediments of Owens and Mono Lakes in California led to the isolation of a bacterial strain capable of metabolizing amino acids with alternative chirality. According to the phylogenetic analysis, the anaerobic strain BK1 belongs to the genus Tindallia; however, despite the characteristics of other described species of this genus, the strain BK1 was able to grow on D-arginine and Dlysine. Cell morphology of this strain showed straight, motile, non-spore-forming rods with sizes 0.45 x 1.2-3 microns. Physiological characteristics of the strain showed that it is catalase negative, obligately anaerobic, mesophilic, and obligately alkaliphilic. This isolate is unable to grow at pH 7 and requires CO3 (2-) ions for growth. The strain has chemo-heterotrophic metabolism and is able to ferment various proteolysis products and some sugars. It plays the role of a primary anaerobe within the trophic chain of an anaerobic microbial community by the degradation of complex protein molecules to smaller and less energetic molecules. The new isolate requires NaCl for growth, and can grow within the range of 0.5-13 %, with the optimum at 1 % NaCl (w/v). The temperature range for the growth of the new isolate is 12-40 C with optimum at 35 C. The pH range for the growth of strain BK1 occurs between 7.8 and 11.0 with optimum at 9.5. This paper presents detailed physiological characteristics of the novel isolate from Owens Lake, a unique relic ecosystem of Astrobiological significance, and makes an accent on the ability of this strain to utilize L-amino acids.

  19. Influence of in ovo mercury exposure, lake acidity, and other factors on common loon egg and chick quality in Wisconsin.

    PubMed

    Kenow, Kevin P; Meyer, Michael W; Rossmann, Ronald; Gray, Brian R; Arts, Michael T

    2015-08-01

    A field study was conducted in Wisconsin (USA) to characterize in ovo mercury (Hg) exposure in common loons (Gavia immer). Total Hg mass fractions ranged from 0.17 µg/g to 1.23 µg/g wet weight in eggs collected from nests on lakes representing a wide range of pH (5.0-8.1) and were modeled as a function of maternal loon Hg exposure and egg laying order. Blood total Hg mass fractions in a sample of loon chicks ranged from 0.84 µg/g to 3.86 µg/g wet weight at hatch. Factors other than mercury exposure that may have persistent consequences on development of chicks from eggs collected on low-pH lakes (i.e., egg selenium, calcium, and fatty acid mass fractions) do not seem to be contributing to reported differences in loon chick quality as a function of lake pH. However, it was observed that adult male loons holding territories on neutral-pH lakes were larger on average than those occupying territories on low-pH lakes. Differences in adult body size of common loons holding territories on neutral-versus low-pH lakes may have genetic implications for differences in lake-source-related quality (i.e., size) in chicks. The tendency for high in ovo Hg exposure and smaller adult male size to co-occur in low-pH lakes complicates the interpretation of the relative contributions of each to resulting chick quality.

  20. Influence of in ovo mercury exposure, lake acidity, and other factors on common loon egg and chick quality in Wisconsin

    USGS Publications Warehouse

    Kenow, Kevin P.; Meyer, Michael W.; Rossmann, Ronald; Gray, Brian R.; Arts, Michael T.

    2015-01-01

    A field study was conducted in Wisconsin (USA) to characterize in ovo mercury (Hg) exposure in common loons (Gavia immer). Total Hg mass fractions ranged from 0.17 mg/g to 1.23mg/g wet weight in eggs collected from nests on lakes representing a wide range of pH (5.0–8.1) and were modeled as a function of maternal loon Hg exposure and egg laying order. Blood total Hg mass fractions in a sample of loon chicks ranged from 0.84ug/g to 3.86 ug/g wet weight at hatch. Factors other than mercury exposure that may have persistent consequences on development of chicks from eggs collected on low-pH lakes (i.e., egg selenium, calcium, and fatty acid mass fractions) do not seem to be contributing to reported differences in loon chick quality as a function of lake pH. However, it was observed that adult male loons holding territories on neutral-pH lakes were larger on average than those occupying territories on low-pH lakes. Differences in adult body size of common loons holding territories on neutral-versus low-pH lakes may have genetic implications for differences in lake-source-related quality (i.e., size) in chicks. The tendency for high in ovo Hg exposure and smaller adult male size to co-occur in low-pH lakes complicates the interpretation of the relative contributions of each to resulting chick quality.

  1. Double Ring Craters

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A faint double ring crater is seen at upper right in this picture of Mercury (FDS 166601) taken one hour and 40 minutes before Mariner 10's second rendezvous with the planet September 21. Located 35 degrees S. Lat. The outer ring is 170 kilometers (10 miles) across. Double ring craters are common features on Mercury. This particular feature and the bright rayed crater to its left were seen from a different viewing angle in pictures taken by Mariner 10 during its first Mercury flyby last March 29.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  2. Small Impact Crater

    NASA Technical Reports Server (NTRS)

    2005-01-01

    22 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small impact crater with a 'butterfly' ejecta pattern. The butterfly pattern results from an oblique impact. Not all oblique impacts result in an elliptical crater, but they can result in a non-radial pattern of ejecta distribution. The two-toned nature of the ejecta -- with dark material near the crater and brighter material further away -- might indicate the nature of subsurface materials. Below the surface, there may be a layer of lighter-toned material, underlain by a layer of darker material. The impact throws these materials out in a pattern that reflects the nature of the underlying layers.

    Location near: 3.7oN, 348.2oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  3. Stripped Crater Floor

    NASA Technical Reports Server (NTRS)

    2004-01-01

    10 February 2004 This full-resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows details on the floor of an ancient meteor crater in the northeastern part of Noachis Terra. After the crater formed, layers of material--perhaps sediment--were deposited in the crater. These materials became somewhat solidified, but later were eroded to form the patterns shown here. Many windblown ripples in the scene indicate the presence of coarse-grained sediment that was not completely stripped away by wind. The picture is located near 22.1oS, 307.0oW. Sunlight illuminates this scene from the left/upper left; the image covers an area 3 km (1.9 mi) wide.

  4. Polygons on Crater Floor

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-357, 11 May 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows a pattern of polygons on the floor of a northern plains impact crater. These landforms are common on crater floors at high latitudes on Mars. Similar polygons occur in the arctic and antarctic regions of Earth, where they indicate the presence and freeze-thaw cycling of ground ice. Whether the polygons on Mars also indicate water ice in the ground is uncertain. The image is located in a crater at 64.8oN, 292.7oW. Sunlight illuminates the scene from the lower left.

  5. Craters! A Multi-Science Approach to Cratering and Impacts.

    ERIC Educational Resources Information Center

    Hartmann, William K.; Cain, Joe

    This book provides a complete Scope Sequence and Coordination teaching module. First, craters are introduced as a generally observable phenomena. Then, by making craters and by investigating the results, students gain close-up, hands-on experience with impact events and their products. Real crater examples from the Moon and elsewhere are included…

  6. Khensu Crater on Ganymede

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The dark-floored crater, Khensu, is the target of this image of Ganymede. The solid state imaging camera on NASA's Galileo spacecraft imaged this region as it passed Ganymede during its second orbit through the Jovian system. Khensu is located at 2 degrees latitude and 153 degrees longitude in a region of bright terrain known as Uruk Sulcus, and is about 13 kilometers (8 miles) in diameter. Like some other craters on Ganymede, it possesses an unusually dark floor and a bright ejecta blanket. The dark component may be residual material from the impactor that formed the crater. Another possibility is that the impactor may have punched through the bright surface to reveal a dark layer beneath.

    Another large crater named El is partly visible in the top-right corner of the image. This crater is 54 kilometers (34 miles) in diameter and has a small 'pit' in its center. Craters with such a 'central pit' are common across Ganymede and are especially intriguing since they may reveal secrets about the structure of the satellite's shallow subsurface.

    North is to the top-left of the picture and the sun illuminates the surface from nearly overhead. The image covers an area about 100 kilometers (62 miles) by 86 kilometers (54 miles) across at a resolution of 111 meters (370 feet) per picture element. The image was taken on September 6, 1996 by the solid state imaging (CCD) system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

  7. Crater Floor Yardangs

    NASA Technical Reports Server (NTRS)

    2004-01-01

    1 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of semi-parallel ridges--yardangs--etched by wind into layered sedimentary rock on the floor of an unnamed crater in Terra Cimmeria. Many craters on Mars have been the sites of sedimentation. Over time, these sediments have become lithified. This picture is located near 31.3oS, 214.6oW. The image covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates the scene from the left/upper left.

  8. Concentric Crater Floor

    NASA Technical Reports Server (NTRS)

    2004-01-01

    8 July 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the interior of a typical crater in northern Acidalia Planitia. The floor is covered by material that forms an almost concentric pattern. In this case, the semi-concentric rings might be an expression of eroded layered material, although this interpretation is uncertain. The crater is located near 44.0oN, 27.7oW, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  9. Secrets of the Wabar craters

    USGS Publications Warehouse

    Wynn, Jeffrey C.; Shoemaker, Eugene M.

    1997-01-01

    Focuses on the existence of craters in the Empty Quarter of Saudi Arabia created by the impact of meteors in early times. Mars Pathfinder and Mars Global Surveyor's encounter with impact craters; Elimination of craters in the Earth's surface by the action of natural elements; Impact sites' demand for careful scientific inspections; Location of the impact sites.

  10. Organic matter in sediments of an acidic mining lake as assessed by lipid analysis. Part I: fatty acids.

    PubMed

    Poerschmann, Juergen; Koschorreck, Matthias; Górecki, Tadeusz

    2012-01-01

    Fatty acid (FA) patterns of sediments collected from the bottom of an acidic mine pit lake (AML) at different depths (surface sediment: 0 to 1cm; deep sediment: 4 to 5 cm) were studied to characterize microbial communities and the sources of sedimentary organic matter (SOM). Studies were performed on the molecular level utilizing source-specific, diagnostic FA biomarkers. The biomarker-based approach has been used widely in marine sediment studies, but has not been applied for sediments from AMLs so far. Combined FA concentrations in the surface sediment were higher compared to those in the deep sediment (497 vs. 127 μg g(-1)d.w., respectively). This was related to deposition of autochthonous biomass and higher terrestrial plants onto the surface sediment, as well as--to lesser extent--with higher bacterial activity on the sediment-water interface. The FA distribution in both sediments was characterized by a strong even-over-odd preference and was bimodal in nature: there was a cluster at nC(14)-nC(18) characteristic of chiefly autochthonous (algal and bacterial) SOM production, and another cluster at nC(22-28) related to input from higher plants. The FA distribution in the surface sediment pointed to higher terrestrial input compared to autochthonous contribution to SOM (67%:33%) as an estimate. Fingerprinting of viable bacteria was accomplished through signature FA markers including branched C(15) and C(17) surrogates, cyclopropanoic acids, 3-hydroxy (OH) acids and monounsaturated surrogates with unusual double bond localization. The abundance of Gram-negative bacteria was higher in the surface sediment as evidenced by total diagnostic 3-OH-fatty acids (37 μg g(-1) versus 25 μg g(-1)). Potential source taxa in both sediment layers included acidophilic iron- and sulfur-oxidizing bacteria including Acidithiobacillus ferrooxidans. High abundances of terminally branched C(15) and C(17) surrogates in both sediments pointed to sulfate- and iron-reducing bacteria

  11. Selenographic distribution of apparent crater depth

    NASA Astrophysics Data System (ADS)

    de Hon, R. A.

    If apparent crater depth is a function of crater diameter, then the frequencies of crater depth and diameter should be similar and the distribution of apparent depths of craters on the lunar surface should be random. Apparent depths of complex craters, which range from 0.2 to 4.3 km on the moon, exhibit little correlation with crater diameters. Crater frequency decreases at increasing diameters, but apparent crater depth displays a Gaussian distribution. The average crater depth for all young craters is 1.8 km. The mean depth of craters on the maria is 1.3 km, and the mean depth of craters on the highlands is 2.1 km. A contour map of apparent crater depths exhibits sufficient organization to suggest that the apparent crater depth is correlated to major lunar provinces. In general, regions of shallow craters are associated with basin interiors. Greater apparent depths are associated with highland terrains.

  12. Inter- and intra-annual chemical variability during the ice-free season in lakes with different flushing rates and acid deposition histories.

    PubMed

    Arnott, Shelley E; Dillon, Peter J; Somers, Keith; Keller, Bill

    2003-01-01

    Quantifying chemical variability in different lake types is important for the assessment of both chemical and biological responses to environmental change. For monitoring programs that emphasize a large number of lakes at the expense of frequent samples, high variability may influence how representative single samples are of the average conditions of individual lakes. Intensive temporal data from long-term research sites provide a unique opportunity to assess chemical variability in lakes with different characteristics. We compared the intra- and inter-annual variability of four acidification related variables (Gran alkalinity, pH, sulphate concentration, and total base cation concentration) in four lakes with different flushing rates and acid deposition histories. Variability was highest in lakes with high flushing rates and was not influenced by historic acid deposition in our study lakes. This has implications for the amount of effort required in monitoring programs. Lakes with high flushing rates will require more frequent sampling intervals than lakes with low flushing rates. Consideration of specific lake types should be included in the design of monitoring programs.

  13. Aqueous Alteration of Outcrops on Endeavour Crater on Mars Inferred from Spatially Oversampled CRISM Spectra and Opportunity Rover Data

    NASA Astrophysics Data System (ADS)

    Arvidson, R. E.; Squyres, S. W.; Murchie, S. L.; McLennan, S. M.; Knoll, A. H.; Catalano, J. G.

    2013-12-01

    Spatially-sharpened CRISM hyperspectral imaging data enabled orbital mapping of a subtle (several weight percent) nontronite (Fe+3 dioctahedral smectite) clay signature in a previously unidentified small rock outcrop on the Cape York portion of the rim of the Noachian-aged Endeavour Crater. Opportunity rover data show that the signature corresponds to finely-layered strata (subset of the Whitewater Lake formation) that were uplifted and overlain by Shoemaker formation impact breccias during the Endeavour crater-forming event. Layers within these Whitewater Lake strata are typically less than or about equal to ~1 cm thick and texturally range from muddy sandstones to materials too fine to resolve in the 30 μm/pixel Microscopic Imager data. These rocks are partially covered by thin, glossy dark veneers locally associated with box-like fractures filled with dark veins. The rocks and veneers have basaltic elemental compositions, with higher concentrations in the veneers of elements easily mobilized by water (Zn, S, Cl, and Br). Cross cutting relationships demonstrate that the veneers post-date Ca-sulfate veins that cut through Whitewater Lake rocks and the overlying impact breccias and also post-date relatively large Whitewater Lake boxwork fractures where compositional data indicate extensive aqueous leaching of rocks within the fractures. Weakly acidic groundwater is inferred to have flowed through fractures and permeable layers within the layered Whitewater Lake strata and become neutralized by reactions with the basaltic materials, leaving behind salts and a minor amount of nontronite in the dark veneers. A greater water flux through the large, permeable boxwork fractures is inferred to have locally produced a greater degree of alteration. Three episodes of post-depositional aqueous alteration are thus clearly evident in the investigated strata: formation of Ca-sulfate veins after Endeavour crater formed, significant alteration to produce extensive alteration

  14. Rim of Henry Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 02 April 2002) This portion of the rim of Henry Crater has numerous dark streaks located on the slopes of the inner crater wall. These dark slope streaks have been suggested to have formed when the relatively bright dust that mantles the slopes slides downhill, either exposing a dust-free darker surface or creating a darker surface by increasing its roughness. The topography in this region appears muted, indicating the presence of regional dust mantling. The materials on floor of the crater (middle to lower left) are layered, with differing degrees of hardness and resistance to erosion producing cliffs (resistant layers) and ledges (easily eroded layers). These layered materials may have been originally deposited in water, although deposition by other means, such as windblown dust and sand, is also possible. Henry Crater, named after a 19th Century French astronomer, is 170 km in diameter and is located at 10.9o N, 336.7o W (23.3o E) in a region called Arabia Terra.

  15. Reading 'Endurance Crater'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    This image shows the area inside 'Endurance Crater' that the Mars Exploration Rover Opportunity has been examining. The rover is investigating the distinct layers of rock that make up this region. Each layer is defined by subtle color and texture variations and represents a separate chapter in Mars' history. The deeper the layer, the further back in time the rocks were formed. Scientists are 'reading' this history book by systematically studying each layer with the rover's scientific instruments. So far, data from the rover indicate that the top layers are sulfate-rich, like the rocks observed in 'Eagle Crater.' This implies that water processes were involved in forming the materials that make up these rocks.

    In figure 1, the layer labeled 'A' in this picture contains broken-up rocks that most closely resemble those of 'Eagle Crater.' Layers 'B,C and D' appear less broken up and more finely laminated. Layer 'E,' on the other hand, looks more like 'A.' At present, the rover is examining layer 'D.'

    So far, data from the rover indicates that the first four layers consist of sulfate-rich, jarosite-containing rocks like those observed in Eagle Crater. This implies that water processes were involved in forming the materials that make up these rocks, though the materials themselves may have been laid down by wind.

    This image was taken by Opportunity's navigation camera on sol 134 (June 9, 2004).

  16. Sediment History Preserved in Gale Crater Central Mound

    NASA Technical Reports Server (NTRS)

    2000-01-01

    [figure removed for brevity, see original site]

    While many of the layered outcrops in craters and chasms on Mars are seen as stair-stepped series of cliffs and benches composed of similar materials with similar thicknesses, other layer outcrops are expressed on relatively smooth, rounded slopes as alternating light and dark bands. The best example of this variety of layered sedimentary material is found in southern Holden Crater. Holden is located at 26.5oS, 33.9oW, and has a diameter of 141 km (88 mi). The context picture above, shows that a valley, Uzboi Vallis, enters the crater on its southwestern side. Not too far from where Uzboi Vallis meets Holden Crater, rounded slopes and buttes consisting of alternating light and dark bands are seen. The origin of these layers is not known, but like those found in other craters on Mars, they might have resulted from deposition of sediment in a lake that would have occupied Holden Crater. Alternatively, these are materials deposited by falling out of the air, the same way that volcanic ash is deposited on Earth. The Viking mosaic (above) images are illuminated by sunlight from the upper right. The MOC image (top left) is illuminated from the upper left. North is up.

  17. A Periglacial Analog for Landforms in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.

    2013-01-01

    Several features in a high thermal inertia (TI) unit at Gale crater can be interpreted within a periglacial framework. These features include polygonally fractured terrain (cf. ice-wedge polygons), circumferential patterns of polygonal fractures (cf. relict pingos with ice-wedge polygons on their surfaces), irregularly-shaped and clustered depressions (cf. remnants of collapsed pingos and ephemeral lakes), and a general hummocky topography (cf. thermokarst). This interpretation would imply a major history of water and ice in Gale crater, involving permafrost, freeze-thaw cycles, and perhaps ponded surface water.

  18. Discovery that secondary craters dominate Europa's small crater population

    NASA Astrophysics Data System (ADS)

    Bierhaus, Edward B.

    2004-08-01

    This thesis presents data and analysis that demonstrate secondary craters (craters formed by material ejected from a primary impactor) dominate the small-crater (<1 km) population on Europa. Of the 17,000+ impact craters I measured in high-resolution images that cover only 0.2% of Europa's surface, 90% are clustered. I applied three spatial analysis techniques, including a novel hybrid of Monte Carlo and hierarchical clustering algorithms, to identify the clustered population. Additional analysis suggests that many unclustered craters are also secondaries; the true percentage of secondary craters is at least 95%. Least-squares, non-linear power-law fits to the differential (dN = kDb dD) size-distributions demonstrate that the secondaries have “steep” exponents, typically b < -4. Because the regions examined are at least hundreds of km away from any large primary crater, this is the first robust study of far- field secondary craters (those formed by material ejected at hundreds of m/s to over 1 km/s). I also measured 7,000+ near-field (only several parent crater radii distant) secondaries around Tyre, a 44 km primary crater on Europa, and measured 1,000+ near-field secondaries in a smaller area around Pwyll, a 26 km primary. The Pwyll data indicate a peak size for the near-field secondaries; the size-distribution at diameters larger than the peak size has very steep exponents, -6.3 to -7.8. The combined measurements of near- and far-field secondaries demonstrate that primary cratering events are extraordinarily efficient in generating ejecta for both populations. This research is the first to demonstrate that, at least on Europa, distant secondary craters overwhelm the small primary craters. Among the many potential implications of my research, two are profound: (1)the population of objects (now known to be ecliptic comets) that hits Europa to form primary craters must have a shallow (b > -2) size- distribution for objects <100 m diameter; and (2)to the degree

  19. Crater Wall and Floor

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    3D Projection onto MOLA data [figure removed for brevity, see original site]

    The impact crater observed in this THEMIS image taken in Terra Cimmeria suggests sediments have filled the crater due to the flat and smooth nature of the floor compared to rougher surfaces at higher elevations. The abundance of several smaller impact craters on the floor of the larger crater indicate however that the flat surface has been exposed for an extended period of time. The smooth surface of the crater floor and rougher surfaces at higher elevations are observed in the 3-D THEMIS image that is draped over MOLA topography (2X vertical exaggeration).

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude -22.9, Longitude 155.7 East (204.3 West). 19 meter/pixel resolution.

  20. Europa's Pwyll Crater

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This view of the Pwyll impact crater on Jupiter's moon Europa taken by NASA's Galileo spacecraft shows the interior structure and surrounding ejecta deposits. Pwyll's location is shown in the background global view taken by Galileo's camera on December 16, 1997. Bright rays seen radiating from Pwyll in the global image indicate that this crater is geologically young. The rim of Pwyll is about 26 kilometers (16 miles) in diameter, and a halo of dark material excavated from below the surface extends a few kilometers beyond the rim. Beyond this dark halo, the surface is bright and numerous secondary craters can be seen. The closeup view of Pwyll, which combines imaging data gathered during the December flyby and the flyby of February 20, 1997, indicates that unlike most fresh impact craters, which have much deeper floors, Pwyll's crater floor is at approximately the same level as the surrounding background terrain.

    North is to the top of the picture and the sun illuminates the surface from the northeast. This closeup image, centered at approximately 26 degrees south latitude and 271 degrees west longitude, covers an area approximately 125 by 75 kilometers (75 by 45 miles). The finest details that can be discerned in this picture are about 250 meters (800 feet) across. This image was taken on at a range of 12,400 kilometers (7,400 miles), with the green filter of Galileo's solid state imaging system.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  1. Influence of Acid Mine Drainage (AMD) on recent phyto- and zooplankton in "the Anthropogenic Lake District" in south-west Poland

    NASA Astrophysics Data System (ADS)

    Sienkiewicz, Elwira; Gasiorowski, Michal

    2015-04-01

    In south-west Poland (central Europe) many the post-mining lakes formed so-called "the Anthropogenic Lake District". Areas, where water comes in contact with lignite beds characterized by high concentration of sulfide minerals are called Acid Mine Drainage (AMD). Pyrite oxidation and other sulfide compounds caused release sulfuric acids and heavy metal ions. These processes caused decline of water pH, sometimes to extremely low pH < 2.8. Presently, pit lakes located in south-west Poland have water pH ranged between 2.7 and 8.9. Differences of water reaction in the mine lakes depend on many factors, such as bedrock buffer capacity, geological structure of carboniferous area, exploitation technique of lignite, methods of filling and water supply of reservoirs and their age. During the evolution of lakes' ecosystems, sulfate-iron-calcium type of waters occurring in acid lakes will transform in alkaline hydrogen-carbonate-calcium type of waters. Due to the different time of the completion of lignite exploitation, lakes' age varied between forty and over one hundred years. Studies showed that younger <